WO2021218505A1

WO2021218505A1 - Laser-radar transmitting apparatus, laser radar, and detection method

Info

Publication number: WO2021218505A1
Application number: PCT/CN2021/082798
Authority: WO
Inventors: 高玉荣; 向少卿
Original assignee: 上海禾赛科技股份有限公司
Priority date: 2020-04-30
Filing date: 2021-03-24
Publication date: 2021-11-04

Abstract

A laser-radar transmitting apparatus (10), a laser radar, a detection method for a laser radar, a tunable laser device and a control method therefor. The laser-radar transmitting apparatus comprises: a laser transmitting unit (11), wherein the laser transmitting unit (11) is configured to be able to output a laser with a hopping wavelength; a chromatic dispersion unit (12), wherein the chromatic dispersion unit (12) is disposed downstream of a light path of the laser transmitting unit (11), and is configured to be able to receive the laser and make the laser emit in different directions according to different wavelengths of the laser, so as to obtain scanning of the laser in a first plane; and a one-dimensional scanning unit (13), wherein the one-dimensional scanning unit (13) is disposed downstream of a light path of the chromatic dispersion unit (12) and receives the laser from the chromatic dispersion unit (12), so as to obtain scanning of the laser in a second plane, with the first plane being perpendicular to the second plane.

Description

Laser radar launching device, laser radar and detection method

Technical field

The present disclosure generally relates to the field of optoelectronic technology, and in particular to a laser radar transmitting device, a laser radar including the transmitting device, and a laser radar detection method.

Background technique

In recent years, autonomous driving technology has developed rapidly, and lidar has become indispensable as its core sensor for distance sensing. At present, the scanning methods in vehicle-mounted lidar mainly include mechanical scanning, galvanometer scanning and phased array. Mechanical scanning has low reliability and slow speed due to the use of mechanical rotating parts. Although phased array radar can achieve high-speed scanning, it is still in the experimental research stage. Lidar based on two-dimensional galvanometer scanning can achieve high-speed and high-resolution scanning to a certain extent. However, in the lidar based on the two-dimensional galvanometer scanning scheme (such as FMCW radar), if the optical fiber is used, since the receiving delay angle is proportional to the detection distance and the scanning angular velocity, as the distance increases, the delay angle becomes larger and larger, and the scanning The greater the angular velocity, the greater the delay angle at the same time. The delay angle causes the beam spot of the echo at the end of the fiber to tilt and shift, which in turn leads to a decrease in receiving efficiency. In the current two-dimensional galvanometer scanning scheme, due to the high frequency of the galvanometer's fast axis and the fast scanning angular velocity, even after a short period of time, when the laser spot emitted and then returned to the fiber, it has already deviated, and The echo can no longer be received efficiently. On the other hand, during the rapid scanning of the galvanometer, serious dynamic speckle modulation will be caused. For FMCW lidar, the mutual interference between echo and local oscillator is essentially weakened, which is manifested as a decrease in the signal-to-noise ratio. The present invention aims to solve the above-mentioned problems. The solution of the present invention is to reduce the frequency (speed) of the scanning mirror under the premise of ensuring the high-speed scanning of the lidar system, so that the scanning mirror has a smaller deflection during a detection process, and the echo spot can continue to return to the optical fiber to achieve high Scan efficiently and improve the signal-to-noise ratio.

In addition, existing lasers generally consist of three parts: First, the gain medium. The gain medium is the material that generates stimulated radiation in the laser, and can achieve energy level transitions. At present, there are thousands of gain media for lasers, and the laser wavelength ranges from X-ray to infrared light. Second, the source of motivation. The role of the excitation source is to give energy to the gain medium, that is, the external energy that excites atoms from a low energy level to a high energy level. Incentive sources usually include light energy, thermal energy, electric energy, chemical energy, etc. Third, the optical resonant cavity is a pair of mirrors with high reflectivity installed at both ends of the gain medium, one of which is a total reflection mirror and the other is a partial reflection mirror. The function of the optical resonant cavity is to make the stimulated radiation of the gain medium go on continuously; the second is to continuously accelerate the photons; the third is to limit the direction of the laser output.

The specific process of laser working is: the excitation source supplies the gain medium energy, so that the particles in the ground state are pumped to a high-energy state after obtaining a certain amount of energy, forming a population inversion on the two energy levels. The specific wavelength of fluorescence generated by the gain medium, or the externally incident seed light of a specific wavelength, causes the gain medium in the inverted distribution to generate stimulated radiation. When the generated stimulated radiation reaches the mirrors at both ends, it will be reflected back to the gain again. Medium, thereby continuing to induce new stimulated radiation. The further amplified stimulated radiation is reflected back and forth in the resonant cavity, and at the same time, new stimulated radiation is continuously induced, which makes it avalanche-like to be amplified to generate a strong laser, which is output from one end of the partial reflector.

Although the commonly used tunable lasers on the market have fast tuning speed, their wavelength is usually continuously adjustable and the tuning range is small, resulting in a small scanning range of the emitted laser beam after dispersion, which is not suitable for vehicle-mounted laser radars. However, lasers that realize large-scale tunable generally need to introduce temperature adjustment. Because the temperature adjustment speed is slow, it cannot meet the requirements of fast scanning of the vehicle-mounted lidar.

The content of the background technology is only the technology known to the inventor, and does not of course represent the existing technology in the field.

Summary of the invention

In view of at least one problem in the prior art, the present invention provides a laser radar transmitting device, including:

A laser emitting unit, the laser emitting unit is configured to output a laser whose wavelength can be hopped;

Dispersion unit, the dispersive unit is arranged downstream of the optical path of the laser emitting unit, and is configured to receive the laser, and according to the wavelength of the laser, the laser is emitted in different directions to obtain the The scanning of the laser in the first plane; and

A one-dimensional scanning unit, the one-dimensional scanning unit is arranged downstream of the optical path of the dispersive unit and receives the laser from the dispersive unit to obtain a scan of the laser in a second plane, wherein the first plane is vertical On the second plane.

According to an aspect of the present invention, the dispersive unit includes a grating, and the wavelength-hopable laser light is emitted at the -1 level or the +1 level of the grating.

According to an aspect of the present invention, the one-dimensional scanning unit is a one-dimensional galvanometer, a swing mirror or a rotating mirror.

According to an aspect of the present invention, the laser emitting unit includes a tunable laser, and the tunable laser includes:

Excitation source, which can output excitation;

A gain unit, the gain unit is located downstream of the excitation source and receives excitation from the excitation source to generate stimulated radiation;

The first reflecting mirror and the second reflecting mirror, wherein the second reflecting mirror is a partially transmissive reflecting mirror, wherein the first reflecting mirror and the second reflecting mirror form a laser resonant cavity, and the gain unit is located in the laser In the resonant cavity, a laser oscillation of a specific wavelength is formed in the laser resonant cavity, and the laser light generated in the laser resonant cavity is emitted from the second mirror to form an outgoing laser;

FP etalon, the FP etalon is arranged in the laser resonator to adjust the wavelength of the emitted laser,

Wherein the laser resonator has multiple longitudinal modes, the FP etalon has multiple transmission peaks, and the gain unit is configured to change the longitudinal mode of the laser resonator so that one of the transmission peaks and one of the longitudinal modes It is basically matched, and the transmission peak that establishes the matching relationship can be changed, thereby changing the wavelength of the emitted laser light.

According to an aspect of the present invention, the gain unit is configured to change the cavity length of the laser resonant cavity by changing the current injected into the gain unit, thereby changing the longitudinal mode of the laser resonant cavity.

According to an aspect of the present invention, the laser emitting unit further includes a control unit connected to the gain unit and injecting current into the gain unit, and the control unit is configured to inject current into the gain unit to One of the longitudinal modes of the laser resonator is basically matched with one of the transmission peaks of the FP etalon, and different currents can be injected into the gain unit so that the different transmission peaks of the FP etalon are One longitudinal mode is basically matched, thereby changing the wavelength of the outgoing laser.

According to an aspect of the present invention, the FP etalon is arranged obliquely with respect to the normal of the first mirror and the second mirror.

According to an aspect of the present invention, the laser emitting unit further includes a tunable filter, and the tunable filter is disposed in the laser resonant cavity to adjust the wavelength range of the emitted laser light.

According to an aspect of the present invention, the laser emitting unit includes a plurality of lasers, and the wavelengths of the plurality of lasers are different from each other.

According to one aspect of the present invention, the emitting device further includes a laser driving unit connected to the laser emitting unit and configured to drive the laser emitting unit to output the wavelength hopping in a certain time sequence. Become the laser.

The present invention also provides a laser radar transmitting device, including:

A rotary drive unit configured to drive the laser emitting unit and the dispersive unit to rotate around a rotation axis to obtain a scan of the laser light from the dispersive unit in a second plane, wherein the first The plane is perpendicular to the second plane, and the rotation axis is parallel to the first plane.

Excitation source, which can output excitation;

According to one aspect of the present invention, the FP etalon is arranged obliquely with respect to the normals of the first and second mirrors, wherein the laser emitting unit further includes a tunable filter, and the tunable The filter is arranged in the laser resonant cavity to adjust the wavelength range of the emitted laser light.

The present invention also provides a laser radar, including:

The launching unit as described above, the launching unit is configured to emit a detection laser for detecting a target;

A receiving unit, the receiving unit includes a photodetector configured to receive the echo of the detection laser diffusely reflected on the target, and convert it into an electrical signal;

A signal processing unit, which is coupled to the receiving unit, and generates a point cloud of the lidar according to the electrical signal.

According to an aspect of the present invention, the receiving unit further includes a receiving lens and an optical fiber, one end surface of the optical fiber is located at the focal plane of the receiving lens, and the receiving lens condenses the echo to the optical fiber. One end face is coupled into the optical fiber, and the echo is emitted through the other end face of the optical fiber and received by the photodetector.

The present invention also provides a detection method of lidar, including:

Drive a laser emitting unit to output a laser whose wavelength can be hopped;

The laser is received by a dispersion unit, and the laser is emitted in different directions according to the wavelength of the laser, so as to obtain the scanning of the laser in the first plane; The downstream one-dimensional scanning unit receives the laser light from the dispersion unit to obtain a scan of the laser light in a second plane, wherein the first plane is perpendicular to the second plane; and

The echo reflected by the laser on the target is received by a photodetector and converted into an electrical signal.

The present invention also provides a detection method of lidar, including:

Drive a laser emitting unit to output a laser whose wavelength can be hopped;

Receiving the laser light by a dispersion unit, and making the laser light emit in different directions in the first plane according to the wavelength of the laser light, so as to obtain the scanning of the laser light in the first plane;

The laser emitting unit and the dispersion unit are driven to rotate around a rotation axis to obtain a scan of the laser light from the dispersion unit in a second plane, wherein the first plane is perpendicular to the second plane, and the rotation The axis is parallel to the first plane; and

The present invention also provides a tunable laser, including:

Excitation source, which can output excitation;

According to one aspect of the present invention, the tunable laser further includes a control unit that is connected to the gain unit and injects current into the gain unit, and the control unit is configured to inject current into the gain unit to One of the longitudinal modes of the laser resonator is basically matched with one of the transmission peaks of the FP etalon, and different currents can be injected into the gain unit so that the different transmission peaks of the FP etalon are One longitudinal mode is basically matched, thereby changing the wavelength of the outgoing laser.

According to one aspect of the present invention, the tunable laser further includes a tunable filter, and the tunable filter is arranged in the laser resonator to adjust the wavelength range of the emitted laser light.

According to one aspect of the present invention, the excitation source includes a pump unit that can generate pump light or pump current, and the tunable laser further includes a collimator disposed between the gain unit and the FP etalon A lens to collimate the light beam emitted from the gain unit and then enter the FP etalon.

The present invention also provides a control method of a tunable laser, including:

Generate incentives through incentive sources;

The excitation is received by a gain unit to generate stimulated radiation, wherein the gain unit is located in a laser resonant cavity, the laser resonant cavity includes a first mirror and a second mirror, and the second mirror is partially transmissive The reflector, forming a laser oscillation of a specific wavelength in the laser resonant cavity, and the laser generated in the laser resonant cavity is emitted from the second reflector; wherein the laser resonant cavity has multiple longitudinal modes, the An FP etalon is arranged in the laser resonant cavity, and the FP etalon has a plurality of transmission peaks;

Changing the longitudinal mode of the laser resonant cavity by the gain unit, so that one of the transmission peaks is substantially matched with one of the longitudinal modes;

The transmission peak that establishes the matching relationship is changed by the gain unit, and the wavelength of the emitted laser light is changed.

According to one aspect of the present invention, the step of changing the longitudinal mode of the laser resonant cavity includes: changing the current injected into the gain unit to change the cavity length of the laser resonant cavity, thereby changing the longitudinal mode of the laser resonant cavity.

According to one aspect of the present invention, the step of changing the transmission peak for establishing a matching relationship through the gain unit to change the wavelength of the emitted laser includes: injecting different currents into the gain unit to make the FP etalon have different transmission peaks. It is basically matched with one of the longitudinal modes, thereby changing the wavelength of the emitted laser light.

According to one aspect of the present invention, the control method further includes adjusting the wavelength range of the emitted laser light through a tunable filter arranged in the laser resonant cavity.

According to one aspect of the present invention, the excitation source includes a pump unit that can generate pump light or pump current, and the laser resonant cavity is also provided with a collimator located between the gain unit and the FP etalon. A straight lens to collimate the light beam emitted from the gain unit and then enter the FP etalon.

The present invention also provides a laser radar, including:

A transmitting unit, the transmitting unit includes the tunable laser as described above, and is configured to emit a detection laser beam for detecting a target;

A receiving unit, the receiving unit is configured to receive the echo of the detection laser beam reflected on the target, and convert it into an electrical signal;

A processing unit, which is coupled to the receiving unit, and calculates the distance between the target and the lidar according to the electrical signal.

Description of the drawings

The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 shows a transmitting device according to an embodiment of the first aspect of the present invention;

Figure 2 shows a transmitting device according to another embodiment of the first aspect of the present invention;

Fig. 3 shows a schematic diagram of a tunable laser according to an embodiment of the second aspect of the present invention;

4 shows the matching diagram of the transmission peak of the longitudinal mode of the laser cavity and the F-P etalon according to the second aspect of the present invention;

Figure 5 shows a schematic diagram of a variant of a tunable laser according to the second aspect of the present invention;

Fig. 6 shows a schematic diagram of a tunable laser according to another embodiment of the second aspect of the present invention;

Fig. 7 shows a flow chart of a control method of a tunable laser according to an embodiment of the second aspect of the present invention;

Fig. 8 shows a block diagram of a lidar according to an embodiment of the present invention;

Figure 9 shows a receiving unit according to a preferred embodiment of the third aspect of the present invention;

Figure 10 shows the structure of a lidar according to an embodiment of the third aspect of the present invention;

FIG. 11 shows a schematic diagram of a point cloud obtained by scanning by a conventional lidar;

Fig. 12 shows a schematic diagram of a point cloud obtained by scanning a lidar according to the third aspect of the present invention;

FIG. 13 shows a detection method of lidar according to an embodiment of the third aspect of the present invention; and

Fig. 14 shows a laser radar detection method according to another embodiment of the third aspect of the present invention.

Detailed ways

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art can realize, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise" and other directions or The positional relationship is based on the position or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the pointed device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more than two, unless otherwise specifically defined.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected or integrally connected: It can be mechanically connected, or electrically connected or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, which can be the internal communication of two components or the interaction of two components relation. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise clearly defined and defined, the "on" or "under" of the first feature of the second feature may include the first and second features in direct contact, or may include the first and second features Not in direct contact but through other features between them. Moreover, the "above", "above", and "above" of the first feature on the second feature include the first feature directly above and diagonally above the second feature, or it simply means that the first feature is higher in level than the second feature. The “below”, “below” and “below” of the first feature of the second feature include the first feature directly above and diagonally above the second feature, or it simply means that the level of the first feature is smaller than the second feature.

The following disclosure provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention may repeat reference numerals and/or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and/or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and/or the use of other materials.

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not used to limit the present invention.

first

The first aspect of the present invention relates to a launching device that can be used for lidar, which is described in detail below with reference to FIG. 1.

As shown in FIG. 1, the emitting device 10 includes a laser emitting unit 11, a dispersion unit 12 and a one-dimensional scanning unit 13. The laser emitting unit 11 is configured to output laser light whose wavelength can be hopped. The dispersion unit 12 is arranged downstream of the optical path of the laser emitting unit 11, and is configured to receive the laser, and according to the wavelength of the laser, emit the laser in different directions to obtain the The scanning of the laser in the first plane. The one-dimensional scanning unit 13 is arranged downstream of the optical path of the dispersion unit and receives laser light from the dispersion unit to obtain scanning of the laser light in a second plane, wherein the first plane is perpendicular to the first plane. Two planes. When used in lidar, the first plane is, for example, a vertical plane, and the second plane is, for example, a horizontal plane, and vice versa.

The laser emitting unit 11 may include a plurality of lasers, and the wavelength corresponding to each laser is different from each other, so that the laser emitting unit 11 can output laser light whose wavelength can be hopped according to a preset time sequence. In addition or alternatively, the laser emitting unit 11 may include a tunable laser whose output wavelength can be discretely tuned, so as to realize the jump of the wavelength of the output laser. The preferred embodiment of the laser will be described in the second aspect below. The emitting device 10 may further include a laser driving unit connected to the laser emitting unit 11 and configured to drive the laser emitting unit to output the laser light whose wavelength can be hopped in a certain time sequence.

In addition, as shown in FIG. 1, the emitting device 10 preferably further includes a collimating device 14, for example, a convex lens, which is located between the laser emitting unit 11 and the dispersion unit 12. The laser emitting unit 11 is located on the focal plane of the collimating device 14 so that the laser beam emitted by the laser emitting unit 11 can be collimated and then incident on the dispersion unit 12.

The dispersion unit 12 may be any type of spatial angular dispersion device, including but not limited to gratings, prisms, etc., as long as the direction of the corresponding emitted light is different according to the wavelength of the incident light. As shown schematically in FIG. 1, the laser light emitted by the laser emitting unit 11 is collimated by the collimating device 14 and then incident on the dispersion unit 12. Depending on the wavelength of the laser, after passing through the dispersion unit 12, the corresponding exit angle is also different. As shown in Figure 1, when the laser wavelengths are λ ₁ and λ ₂ respectively, the corresponding exit directions are also different. According to a preferred embodiment of the present invention, the dispersion unit 12 is a grating, and the direction of the +1 order or the -1 order diffraction of the grating can be used as the emission direction of the laser light. If the center wavelength of the tunable laser of the laser emitting unit 11 is λ=1550nm, the laser output from the laser is collimated by the collimator 14 and incident on the high-efficiency grating with the ^{grating constant d=1201 -1 mm at the incident angle θ} , According to the grating equation, the exit angle γ of the beam satisfies:

Where m is the diffraction order, and first order diffraction is used in this example, that is, m=1. When the laser emitting unit 11 includes a discretely tunable laser, by adjusting the laser injection current, the laser can output laser light whose wavelength can be hopped (non-continuously) according to a preset time sequence. When the incident angle is 63°, the output laser frequency varies from 0 (center wavelength 1550nm corresponds to 0Hz) to 1THz, and the interval is 100GHz. According to the above grating equation, the emission angle after grating dispersion is 76.06° to 78.56°, with a variation range of 2.5 °, the interval is 0.25°. Because the laser current adjustment response is very fast, it can realize fast and wide-range beam static scanning. In this embodiment, the light beam of each wavelength exits at a certain angle after passing through the grating, and the scanning in the vertical plane in FIG. 1 is realized by adjusting the output wavelength of the laser. The above-mentioned frequency variation range is merely indicative, and a scanning interval of, for example, 0.1° can also be achieved by adjusting the laser current. How to adjust the laser injection current to achieve a laser whose output wavelength can be jumped will be described in detail below.

According to a preferred embodiment of the present invention, the one-dimensional scanning unit 13 is a one-dimensional galvanometer, a swing mirror or a rotating mirror. Lidar usually requires detection and scanning in two dimensions. For example, it has a certain detection range in the vertical direction, such as a vertical field of view of 60 degrees, and needs to scan in the horizontal direction, such as a 360-degree rotation scan or less than Scan back and forth within 360 degrees. In this embodiment, the dispersion unit 12 and the one-dimensional scanning unit 13 respectively implement scanning in one of the dimensions. According to a preferred embodiment of the present invention, the dispersion unit 12 realizes scanning in a vertical plane, while the scanning unit 13 realizes scanning in a horizontal direction or a horizontal plane. Of course, the opposite setting can also be carried out.

As shown in FIG. 1, according to the wavelength of the laser light emitted by the laser emitting unit 11, the direction of the probe beam emitted from the dispersion unit 12 in the vertical plane is also different. The scanning unit 13 has, for example, a rotation axis OX. The rotation axis OX is along a vertical direction, that is, perpendicular to the horizontal plane. The scanning unit 13 rotates around its rotation axis to scan and reflect the probe beam incident on it along different angles in the horizontal plane. Galvo mirrors, swing mirrors or rotating mirrors are common optical devices, and their specific structure and control will not be repeated here.

In the above structure, the laser light emitted from the tunable laser reaches the dispersive unit at a fixed incident angle after passing through the collimating device. Since the emitting angle of the dispersive unit is related to the wavelength and incident angle of the incident light, under the same incident angle, adjust The output wavelength of the laser can change the angular distribution of the beam in space, realizing a beam scanning scheme based on a tunable laser combined with a dispersive unit. Since the invention adopts a wavelength hopping (discrete tuning) laser, a larger static scanning range is realized. At present, the wavelength adjustment range of a continuously tuned laser is within 1 nm, and the above-mentioned 1THz frequency change corresponds to a wavelength adjustment range of about 8 nm.

In the laser radar transmitting device shown in FIG. 1, a one-dimensional scanning unit 13 such as a galvanometer or a rotating mirror is used to realize scanning in the second plane. The present invention is not limited to this, and other methods can also be used to realize scanning in the second plane. Fig. 2 shows a transmitting device 20 according to a preferred embodiment of the present invention. In addition to the laser emitting unit 11, the dispersion unit 12, and the collimating device 14, a rotation driving unit 23 is also included. The rotation driving unit 23 is configured to drive the laser emitting unit 11 and the dispersion unit 12 to rotate around the rotation axis XX to obtain the scanning of the laser light from the dispersion unit 12 in the second plane, wherein the first A plane is perpendicular to the second plane, and the rotation axis XX is parallel to the first plane. Those skilled in the art can easily conceive various implementations of the rotation drive unit 23. For example, it may include a rotating motor and a turntable, and the turntable is fixed on the output shaft of the rotating motor so that it can be driven to rotate by the rotating motor. The laser emitting unit 11, the dispersion unit 12, and the collimating device 14 are carried on the turntable so as to rotate with the rotation of the turntable. Similar to the embodiment in FIG. 1, the dispersion unit 12 realizes the scanning of the detection laser beam in the vertical plane, and realizes the vertical detection field of view of the lidar; the rotation driving unit 23 realizes the scanning in the horizontal plane.

In addition, the present invention does not limit the scanning range in the horizontal plane, and it can be completely determined according to the type and requirements of the lidar. For example, if you need to scan a 360-degree horizontal field of view, you can use a rotary drive unit 23 that can rotate 360 degrees; if you need a 60-degree horizontal field of view, you can make the rotary drive unit 23 swing back and forth within a range of 60 degrees. These are all within the protection scope of the present invention. In addition, the rotation speed can be set as required, for example, a uniform motion can be selected, or a preset motion curve can be followed, for example, a sinusoidal motion curve can be followed.

Second aspect

The second aspect of the present invention relates to a laser, as shown in the

lasers

100, 101, and 200 described below. The laser of the second aspect of the present invention can be used as the laser of the laser emitting unit 11 in the above first aspect, thereby generating laser light whose wavelength can be hopped (non-continuous). It will be described in detail below with reference to the drawings.

Fig. 3 shows a schematic diagram of a tunable laser according to an embodiment of the present invention. The tunable laser 100 will be described in detail below in conjunction with FIG. 3. As shown in the figure, the tunable laser 100 includes an excitation source 1, a gain unit 2, a first mirror 3, a second mirror 4 and an FP etalon 5. The excitation source 1 is configured to output excitation, and its function is to provide energy to the gain unit 2. Excitation usually includes optical pumping, electrical pumping, etc., and can provide external energy that excites the atoms of the gain unit 2 from a low energy level to a high energy level. The gain unit 2 is located downstream of the excitation source 1 and receives excitation (for example, optical/electric excitation) from the excitation source 1 to generate stimulated radiation. The gain unit 2 includes a laser gain medium to achieve population inversion to form optical amplification. The laser gain medium in the gain unit 2 is related to the wavelength of the laser light generated by the laser. The laser gain medium may be a gallium arsenide semiconductor or an I nP-based semiconductor, and the center wavelength is, for example, 1550 nm.

The excitation source 1 outputs light/electric excitation to supply energy to the gain unit 2, so that the particles in the ground state are pumped to a high-energy state after obtaining a certain amount of energy, forming a population inversion on the two energy levels. The fluorescent light of a specific wavelength generated by the gain unit 2 or the seed light of a specific wavelength incident from the outside causes the gain unit in the inverted distribution to generate stimulated radiation. One of the first mirror 3 and the second mirror 4 is a partially transmissive mirror, and its transmission ratio is relatively small, for example, between 2% and 5% or lower. According to a preferred embodiment of the present invention, the first reflector 3 is a total reflector, that is, the light beam incident on the first reflector 3 in the laser cavity is completely reflected or nearly completely reflected; The second mirror 4 is a partially transparent mirror, and the transmittance is, for example, between 2% and 5% or lower. The reflective surfaces of the first mirror 3 and the second mirror 4 are opposed to each other, thereby forming a laser resonant cavity in the opposing space, and the gain unit 2 is located in the laser resonant cavity, so that the stimulated radiation A laser oscillation of a specific wavelength is formed in the laser resonant cavity, and the laser light generated in the laser resonant cavity is emitted from the second mirror to form an outgoing laser. Specifically, when the generated stimulated radiation reaches the mirror surfaces of the first mirror 3 and the second mirror 4, it will be reflected back to the gain unit again, thereby continuing to induce new stimulated radiation. The further amplified stimulated radiation is reflected back and forth in the laser resonator formed between the first mirror 3 and the second mirror 4, and at the same time, it continuously induces new stimulated radiation, making it amplified like an avalanche, resulting in a strong The strong laser light is finally output from one end of the second mirror 4. The laser resonant cavity can make the photons in the cavity have the same frequency, phase and running direction, so that the laser has good directivity and coherence. The wavelength of the laser that forms the oscillation is related to the length of the resonant cavity. The mode is related to the length of the laser cavity and is used to describe the laser frequency. In theory, the laser resonator can generate countless equally spaced frequencies of light, but because the gain medium only produces the maximum gain for the light of a specific frequency, and the light of other frequencies is suppressed, the laser generally only outputs the laser of a specific frequency. The longitudinal mode refers to the frequency, that is to say, assuming that the laser selects the first longitudinal mode (that is, corresponding to the first wavelength λ1) to emit the laser for the first time, the laser with the wavelength λ1 is emitted.

The FP etalon 5 is arranged in the laser resonant cavity to adjust the wavelength of the emitted laser light. Preferably, the tunable laser 100 further includes a collimating lens 6. As described above, the light beam emitted from the gain unit 2 is collimated by the collimator lens 6 and then enters the FP etalon 5, passes through the FP etalon 5, and reaches the second mirror 4 and is reflected by the second mirror. According to the phase matching condition of laser resonance, corresponding to the cavity length of a specific laser resonator, only the laser of a specific wavelength can oscillate in the laser resonator and be emitted to form an outgoing laser. Since the FP etalon 5 itself also has periodic transmission peaks, the maximum gain output can be obtained only when the longitudinal mode of the laser cavity and the transmission peak of the FP etalon 5 are basically completely matched. Therefore, the laser output of a specific wavelength can be selected by accurately adjusting the cavity length of the laser resonant cavity. Therefore, in the present invention, the FP etalon 5 is equivalent to adding a frequency (wavelength) selection device to the laser resonator. The transmittance of the FP etalon changes periodically with the frequency (wavelength), and at a certain frequency (wavelength) There are multiple transmission peaks in the range of ), and the laser cavity usually has multiple longitudinal modes. In the present invention, the gain unit 2 is configured to change the longitudinal mode of the laser cavity (that is, change the frequency corresponding to the longitudinal mode), so that One of the transmission peaks is basically matched with one of the longitudinal modes, and by changing the transmission peak that establishes the matching relationship, the frequency and wavelength of the outgoing laser are changed to achieve wavelength hopping. The following is described with reference to FIG. 4.

Fig. 4 shows a frequency matching diagram of a longitudinal mode of a laser cavity and an FP etalon according to an embodiment of the present invention. As shown in the figure, the abscissa represents the frequency, the ordinate represents the amplitude, the curve W1 represents the longitudinal mode of the laser resonator, and the curve W2 represents the transmission curve of the FP etalon. As shown in Fig. 4, the laser resonator has multiple longitudinal modes, such as periodic. The FP etalon also has multiple transmission peaks, which may also be periodic. When the longitudinal mode of the laser resonator cavity coincides with the transmission peak of the FP etalon, the corresponding frequency is the frequency of the laser that can finally be emitted through the second mirror 4, and the wavelength of the emitted laser can be known. According to the embodiment of the present invention, after the specification of the FP etalon is determined, its transmission peak on the frequency spectrum is determined, and the multiple longitudinal modes of the laser resonator can move left and right on the frequency spectrum, for example, by the cavity length The adjustment of the cavity length of the resonant cavity can be achieved, for example, by the gain unit 2, which will be described in detail below.

For the first moment, refer to the first picture in Fig. 4, where the longitudinal mode of the laser resonator with a frequency of 20 GHz and the transmission peak of the FP etalon appear (center) coincide, and the laser wavelength λ1 at this frequency is output; what needs to be explained is , The above figure is the longitudinal mode selection based on the center wavelength (such as 1550nm), the center wavelength corresponds to 0GHz in the above figure, for example, according to the wavelength-frequency relationship C=λf, where C is the speed of light and f is the output laser Frequency, λ is the output laser wavelength, the laser wavelength λ1 at this time can be obtained. At the second moment, refer to the second graph in Figure 4. The gain unit 2 changes the longitudinal mode of the laser resonator, causing the curve W1 to shift to the left, while the curve W2 remains unchanged. The longitudinal mode of the laser cavity with a frequency of 40 GHz and the transmission peak of the FP etalon When coincident, the laser wavelength λ2 at this frequency is output; at the second moment, see the third diagram in Fig. 4, the gain unit 2 continues to change the longitudinal mode of the laser resonator, so that the curve W1 continues to shift to the left, and the curve W2 continues to remain unchanged. The longitudinal mode of the laser resonator with a frequency of 60 GHz coincides with the FP etalon, and the laser wavelength λ3 at this frequency is output. It can be seen that the whole process from the first moment to the third moment realizes the jump tuning of the laser emitted by the laser from the wavelength λ1 to the wavelength λ2 and then to the wavelength λ3. The traditional continuous wavelength tuning corresponds to a small change in frequency around one mode, while the mode hopping of the present invention brings about a wide range of frequency (wavelength) changes. The above figure schematically shows the mode hopping. In practical applications The mode hopping range can be 0 to 1THz.

Fig. 5 shows a schematic diagram of a variant of the tunable laser shown in Fig. 3. As shown in FIG. 5, compared with the tunable laser 100 shown in FIG. 3, the tunable laser 101 includes a control unit 7 in addition to the various components of the tunable laser 100. The gain unit 2 is connected to and injects current into the gain unit 2. The cavity length of the laser resonant cavity can be changed by the current injected into the gain unit 2, so that one of the longitudinal modes of the laser resonator and one of the FP etalons The transmission peaks are basically matched. Therefore, in this embodiment, the control unit 7 injects a current into the gain unit 2 so that one of the longitudinal modes of the laser resonator and one of the transmission peaks of the FP etalon basically match, and can inject different The current is used to make the different transmission peaks of the FP etalon substantially match with one of the longitudinal modes, thereby changing the wavelength of the emitted laser light.

It can be seen from the above that by precisely matching the longitudinal mode of the laser resonator with the transmission peak of the FP etalon 5, discrete tunable lasers can be realized within a specific wavelength range. When the longitudinal mode of the laser resonator changes, the output The laser wavelength will also change as a result. By changing the injection current of the control unit 7 to the gain unit 2, the cavity length of the laser resonant cavity can be changed, thereby changing the longitudinal mode of the laser resonant cavity. Specifically, the gain unit 2 is changed to a small injection current as needed, so that the longitudinal mode of the laser cavity is slightly shifted in FIG. 4, thereby changing the transmission peak of the FP etalon 5 that matches the laser cavity mode, namely The output wavelength of the laser can be changed to an integer multiple of the free spectral region of the FP etalon. For FP etalon 5, its free spectral range can easily reach 100 GHz, so using FP etalon 5, a laser with a tuning range of several nanometers can be realized within a small current change range, and the output wavelength of the laser can be discretely changed . Compared with traditional lasers that use current injection to achieve wavelength changes, the embodiments of the present invention can effectively improve the tunable range of the laser. Compared with the use of components (temperature adjustment) to achieve a tunable laser, the embodiment of the present invention can achieve a rapid and digitally controlled wavelength change by changing the injection current of the laser to perform wavelength tuning. Therefore, it is very suitable for a large field of view. High-frequency scanning lidar system.

In addition, preferably, as shown in FIGS. 3 and 5, the FP etalon 5 in the

tunable lasers

100 and 101 is arranged obliquely with respect to the normals of the first mirror 3 and the second mirror 4. The FP etalon 5 needs to use the transmission peak to select the mode in the laser resonant cavity, in order to prevent the first mirror 3, the second mirror 4 and the end faces of the FP etalon 5 from forming additional resonant cavities, which leads to wavelength tuning. Cause interference, the FP etalon 5 is set not parallel to the first mirror 3 and the second mirror 4, that is, it is inclined relative to the normal of the first mirror 3 and the second mirror 4, and the angle of inclination is based on The wavelength tuning needs to be adjusted.

Fig. 6 shows a schematic diagram of another tunable laser according to an embodiment of the present invention. As shown in the figure, compared with the structure of the tunable laser 100 shown in FIG. 3, the tunable laser 200 further includes a tunable filter 8, and the tunable filter 8 is disposed in the laser resonant cavity. In order to adjust the wavelength range of the outgoing laser, it can be quickly switched to further increase the tuning range of the laser. Preferably, the tunable filter 8 is located between the FP etalon 5 and the second reflector 4.

According to one aspect of the present invention, the excitation source 1 of the

tunable laser

100 or 101 includes a pump unit that can generate pump light. The pump unit is, for example, a pump semiconductor laser diode, which can generate pump light and be incident into the gain unit 2 so that the laser gain medium in the gain unit 2 realizes population inversion. The specific wavelength of fluorescence generated by the gain unit, or the externally incident seed light of specific wavelength, causes the gain medium in the inverted distribution to generate stimulated radiation, and the laser can be amplified and enhanced like an avalanche. In addition, the above-mentioned injecting current to the semiconductor laser chip can also realize the excitation of the gain unit 2.

Fig. 7 shows a flowchart of a control method of a tunable laser according to an embodiment of the present invention. The control method 500 can be used to control the above-mentioned tunable laser 100, tunable laser 101, and tunable laser 200 to adjust the wavelength of the output laser to achieve discrete changes. As shown in the figure, the steps of the control method 500 include:

In step S501: the excitation is generated by the excitation source. The excitation source includes optical pumping, electric pumping, etc. As shown in FIG. 3, the excitation source 1 generates and outputs excitation to supply energy to the gain unit 2.

In step S502: receiving the excitation through a gain unit to generate stimulated radiation, wherein the gain unit is located in a laser resonant cavity, and the laser resonant cavity includes a first mirror and a second mirror, and the second mirror It is a partially transmissive mirror, forming a laser oscillation of a specific wavelength in the laser resonant cavity, the laser generated in the laser resonant cavity is emitted from the second mirror, and the laser resonant cavity has multiple longitudinal modes, so An FP etalon is arranged in the laser resonant cavity, and the FP etalon has a plurality of transmission peaks. The first reflector and the second reflector form a laser resonant cavity in their opposing space, and the particles in the ground state in the gain unit that are set in it and receive light/electric excitation obtain a certain energy and are pumped to a high-energy state. The population reversal of the two energy levels is formed. The fluorescent light of a specific wavelength generated by the gain unit, or the seed light of a specific wavelength incident from the outside, causes the gain unit in the inverted distribution to generate stimulated radiation.

In step S503: the longitudinal mode of the laser resonant cavity is changed by the gain unit, so that one of the transmission peaks is substantially matched with one of the longitudinal modes. When a transmission peak is substantially matched with one of the longitudinal modes, the laser of the frequency corresponding to the transmission peak will be emitted. As mentioned above, according to the phase matching condition of laser resonance, for a specific laser cavity length, only laser light of a specific wavelength can be emitted. That is, when the periodic transmission peak of the FP etalon itself is completely matched with the longitudinal mode of the laser cavity, the matched laser wavelength is emitted from the end of the partial reflector, and this mode obtains the maximum gain output.

In step S504: the transmission peak for establishing the matching relationship is changed by the gain unit, and the wavelength of the emitted laser light is changed. By changing the transmission peak that forms the matching relationship, that is, the transmission peak that matches the longitudinal mode in the laser resonator in step S504 is different from the transmission peak that matches the longitudinal mode in the laser resonator in step S503, so that the output laser can be changed. Frequency (wavelength), so as to achieve the jump of the output laser wavelength.

The above-mentioned control method further includes: changing the current injected into the gain unit to change the cavity length of the laser resonant cavity, thereby changing the longitudinal mode of the laser resonant cavity. Therefore, the laser cavity length can be precisely adjusted by controlling the injection current of the gain unit, and the laser output of a specific wavelength can be selected according to the matching of the longitudinal mode of the laser resonator cavity and the periodic transmission peak of the FP etalon.

The control method as described above, wherein the step of changing the transmission peak that establishes the matching relationship through the gain unit to change the wavelength of the emitted laser includes: injecting different currents into the gain unit to make the FP etalon different transmission The peak is basically matched with one of the longitudinal modes, thereby changing the wavelength of the outgoing laser.

The above-mentioned control method further includes: adjusting the wavelength range of the emitted laser light through a tunable filter arranged in the laser resonant cavity. The tunable filter can be quickly switched to further increase the tuning range of the laser.

The control method as described above, wherein the excitation source includes a pump unit that can generate pump light or pump current. As mentioned above, the pump unit makes the laser gain medium in the gain unit realize the population inversion and generates stimulated radiation.

According to an embodiment of the present invention, the wavelength of the corresponding laser is determined according to the scanning angle of the laser radar in space and the parameters of the dispersive element. Therefore, if the laser radar needs to scan the range, resolution, and dispersive element parameters, the required wavelength can be determined inversely for each angle of the radar, so as to control each laser.

The invention realizes discrete changes of the output wavelength of the tunable laser by adding the FP etalon to the laser. Through the embodiments of the present invention, not only the tunable range of the laser can be effectively improved, but also the rapid and digitally controlled wavelength change can be realized. Because it can achieve fast and wide-range wavelength tuning, the tunable laser of the present invention is very suitable for lidar systems that require a large field of view and high-frequency scanning, and is more widely used.

The present invention also relates to a lidar. Specifically, FIG. 8 shows a block diagram of a lidar 600 according to an embodiment of the present invention. As shown in the figure, the lidar 600 includes a transmitting unit 610, a receiving unit 620, and a processing unit 630. The emitting unit 610 includes one or more tunable laser 100, tunable laser 101 or tunable laser 200 as described above, configured to emit a detection laser beam for detecting the target object OB. The receiving unit 620 is configured to receive the echoes of the detection laser beam reflected on the target OB and convert them into electrical signals. The processing unit 630 is coupled to the receiving unit 620, and calculates the distance between the target OB and the lidar 600 according to the electrical signal. When the lidar 600 is working, the tunable laser 100, the tunable laser 101, or the tunable laser 200 inside the emitting unit 610 emits a laser beam L1 to the surrounding environment, wherein the wavelength of the laser beam L1 can be changed by changing the gain unit The injection current of 2 is changed to achieve wavelength tunability. The wavelength to be adjusted can be calculated inversely according to the preset scanning range and resolution of the lidar 600. The emitted laser beam L1 is projected on the target OB, causing scattering, and a part of the laser beam is reflected back to form an echo L1', which is received by the receiving unit 620 after convergence, and converted into an electrical signal. The processing unit 630 analyzes and calculates the electrical signal to obtain the distance between the target OB and the lidar 600.

Third aspect

The third aspect of the present invention relates to a laser radar, including a transmitting device, a receiving unit, and a signal processing unit. The emitting device is, for example, the emitting device according to the first aspect of the present invention, and the emitting device is configured to emit a detection laser for detecting a target object. The receiving unit includes a photodetector configured to receive the echoes of the detection laser diffusely reflected on the target, and convert them into electrical signals. A signal processing unit, which is coupled to the receiving unit, and generates a laser radar point cloud according to the electrical signal.

FIG. 9 shows a receiving unit 40 according to a preferred embodiment of the present invention, which includes a receiving lens 41, an optical fiber 42 and a photodetector 43. As shown in the figure, one end surface of the optical fiber 42 is located on the focal plane of the receiving lens 41, so that the receiving lens 41 condenses the echo onto the end surface of the optical fiber 42 and couples it into the optical fiber. , The echo is emitted through the other end of the optical fiber and received by the photodetector 43.

In the preferred embodiment of the present invention, a wide-range tunable laser, a dispersion unit, and a one-dimensional scanning unit or a rotation drive unit are combined at the same time. Due to the limited dispersion capability of the dispersion unit, in order to achieve beam scanning with a large field of view, it can work with a large-range tunable laser. Although the current continuous tuning laser based on current tuning has a fast tuning speed, the tuning range is small, resulting in a small scanning range of the beam, which is not suitable for vehicle-mounted laser radars. However, lasers that realize large-scale tunable generally need to introduce temperature adjustment. Because the temperature adjustment speed is slow, it cannot meet the requirements of fast scanning of the vehicle-mounted lidar. In order to solve the above problems, the tunable laser based on mode jump proposed in this solution can achieve fast and large-scale tunability at the same time, which meets the application requirements of static scanning of vehicle-mounted lidar. FIG. 10 shows the structure of a typical lidar 601, which includes the laser emitting unit 11, the collimating device 14, the dispersion unit 12, the one-dimensional scanning unit 13, the receiving unit 18, and the signal processing unit 19 as described above. In addition, the lidar structure further includes a first coupler 15, a second coupler 17 and a circulator 16. The first coupler 15 and the circulator 16 are sequentially arranged between the laser emitting unit 11 and the collimator 14, and the first coupler 15 divides the laser light from the laser emitting unit 11 into two parts according to a preset ratio. For example, according to the ratio of 99:1, most of the laser light enters the collimating device 14 through the circulator 16, and is emitted to the outside of the lidar through the dispersion unit 12 and the one-dimensional scanning unit 13 for target detection ; A small part of the laser light is guided to the second coupler 17. The one-dimensional scanning unit 13 can also be used to receive lidar echoes. The echoes pass through the one-dimensional scanning unit 13, the dispersion unit 12, the collimator 14 and the circulator 16, and then enter the second coupler 17. The second coupler 17 couples the echo with the laser light from the laser emitting unit 11 and makes it incident on the receiving unit 18. The receiving unit 18 includes photodetectors of APD, SPAD(s), S i PM, etc., which can convert incident optical signals into electrical signals. The signal processing unit 19 is coupled to the receiving unit 18, and receives the electrical signal and performs corresponding processing to obtain parameters such as the distance and reflectance of the target. The laser emitting unit 11, the first coupler 15, the second coupler 17, the circulator 16 and the receiving unit 18 are connected by an optical fiber. The emitting end of the circulator 16 is connected with an optical fiber, and the detection laser is emitted from the end face of the optical fiber through a collimating device 14 is collimated and emitted, and the echo of the lidar is converged on the end face of the optical fiber by the collimating device 14.

Through the solution of the present invention, the lateral scanning speed of the one-dimensional scanning unit of the laser radar can be significantly reduced. Details are described below. In the lidar, the dot frequency refers to the time interval between two adjacent scanning points. In the existing scheme and the scheme of the present invention, the dot frequency is 20 microseconds as an example.

In the existing solutions, a two-dimensional galvanometer is usually used, and the two-dimensional galvanometer includes a fast axis and a slow axis that are perpendicular to each other. The fast axis swing realizes scanning in the horizontal plane, and the slow axis swing realizes scanning in the vertical plane, for example. Usually the fast axis frequency can reach 1000 Hz, and the slow axis frequency is tens of Hz. Figure 11 shows a scanning curve. The fast axis is scanned by a triangular wave, and the slow axis is scanned by a sawtooth wave. The scanning sequence is from left to right and from top to bottom. The resolution in the direction is controlled to 0.1 degree, and the resolution in the horizontal direction is controlled to 0.02 degree.

Through the scheme of the preferred embodiment of the present invention, as shown in Fig. 12, scanning is performed in the vertical direction first, and then the horizontal scanning is performed, that is, after the vertical scanning of one column is realized by changing the laser wavelength, the one-dimensional scanning unit (lateral) deflects a certain amount. Angle, and then scan one column vertically. The "mechanical scanning axis" in the horizontal direction in the figure corresponds to the axis OX of the swing mirror or the rotating mirror in FIG. 1, or the rotation axis X-X in FIG. 2, for example. In the existing scheme, the angular interval of every two points in the horizontal direction is 0.02°, and the time interval is 20 microseconds (ie point frequency), which are fixed according to the requirements of the radar system. When scanning with a galvanometer in the existing scheme, every 20 us in the horizontal direction Scan a point and scan it horizontally. However, with the method of this application, a tunable laser is used to emit a laser beam of ten wavelengths in a certain time sequence in the longitudinal direction, and 10 points are scanned by the dispersion unit (a slightly inclined vertical line in the figure is produced), and then The wavelength of the laser is tuned back to the original wavelength, and 10 points are rescanned (to produce an adjacent vertical line with a slight slope). In each cycle, the horizontal angular interval corresponding to 10 points of the vertical scan is still 0.02° (that is, the angular interval between two adjacent points in the horizontal direction is still 0.02°), and the adjacent scanning points The time interval (that is, the dot frequency is still 20us), so the time to complete the scan of 10 points is 200us, that is, the time interval between two adjacent points in the horizontal direction in the figure is 200us, and the scanning speed becomes slower. Taking ten wavelengths as an example, the time for vertical scanning of 10 points is limited. When scanning one point at 20us, the detection time for each point is fixed. So it takes 200us to scan 10 points. That is to say, the lateral scanning angle of 0.02° requires 20us for the existing scheme, but 200us is required for the scheme according to the embodiment of the present invention. Therefore, the angular velocity of the lateral scanning becomes one-tenth of the original one, but the original scheme can still be achieved. The same field of view scanning effect (including resolution, frame rate). If there are 13 wavelengths, that means 13 points in the vertical direction, and the time interval between two adjacent points in the horizontal direction is 260us. The following table lists the comparison between the existing solution and the solution of the present invention.

To	横向分辨率Horizontal resolution	横向两点时间间隔Horizontal two-point time interval	横向角速度Lateral angular velocity
现有方案Existing plan	0.02°0.02°	20us20us	0.02°/20us0.02°/20us
本发明实施例Embodiments of the invention	0.02°0.02°	200us200us	0.02°/200us0.02°/200us

The transmitting device of the first aspect of the present invention is extremely advantageous for a laser radar that uses optical fibers for receiving. In the laser radar based on the two-dimensional galvanometer scanning scheme, if the optical fiber is used for receiving, the receiving delay angle is proportional to the detection distance and the scanning angular velocity. As the distance increases, the delay angle becomes larger and the scanning angular velocity increases. The greater the delay angle at the same time, the delay angle makes the echo spot at the end of the fiber tilt and shift, which in turn leads to a decrease in receiving efficiency. In the current two-dimensional galvanometer scanning scheme, due to the high frequency of the galvanometer's fast axis and the fast scanning angular velocity, even after a short period of time, when the laser spot emitted and then returned to the fiber, it has already deviated, and The echo reception can no longer be performed efficiently. On the other hand, during the rapid scanning of the galvanometer, serious dynamic speckle modulation will be caused. For FMCW lidar, the mutual interference between the echo and the local oscillator is essentially weakened, which results in a decrease in the signal-to-noise ratio. In the present invention, as described above, under the premise of ensuring the high-speed scanning of the lidar system, the frequency (speed) of the scanning mirror is reduced, so that the scanning mirror has a smaller deflection during a detection process, and the echo spot can continue to return to the optical fiber , To achieve high-efficiency scanning and improve the signal-to-noise ratio, improve the receiving efficiency.

The concept of the present invention can be applied to any laser radar system with galvanometer and optical fiber transmitting laser, and is not limited to FMCW laser radar system.

Compared with the existing two-dimensional galvanometer scanning scheme, the spot offset problem caused by the high fast axis frequency, the angular velocity of the scanning device of the present application scheme can be reduced by an order of magnitude, and the resulting decrease in receiving efficiency is almost negligible. At the same time, due to the realization of slow scanning, the dynamic speckle effect is greatly weakened, and the signal-to-noise ratio of the system can be improved. Furthermore, due to the reduction of dynamic speckle effect, the receiving aperture can be increased without affecting the field of view and angular resolution, thereby increasing the detection range.

As shown in FIG. 13, the present invention also relates to a detection method 700 of lidar, including:

In step S701, a laser emitting unit is driven to output a laser whose wavelength can be hopped;

In step S702, the laser is received by a dispersion unit, and the laser is emitted in different directions according to the wavelength of the laser, so as to obtain the scanning of the laser in the first plane;

In step S703, a one-dimensional scanning unit arranged downstream of the optical path of the dispersion unit receives the laser light from the dispersion unit to obtain a scan of the laser light in a second plane, wherein the first plane is perpendicular to the Second plane; and

In step S704, the echo reflected by the laser on the target is received by a photodetector, and converted into an electrical signal.

The detection method can be implemented by, for example, a lidar as described above.

As shown in FIG. 14, the present invention also relates to a detection method 800 of lidar, including:

In step S801, a laser emitting unit is driven to output laser light whose wavelength can be hopped;

In step S802, the laser is received by a dispersion unit, and the laser is emitted in different directions according to the wavelength of the laser, so as to obtain the scanning of the laser in the first plane;

In step S803, drive the laser emitting unit and the dispersive unit to rotate around a rotation axis to obtain a scan of the laser light from the dispersive unit in a second plane, wherein the first plane is perpendicular to the second plane , The rotation axis is parallel to the first plane; and

In step S804, the echo reflected by the laser on the target is received by a photodetector, and converted into an electrical signal.

The detection method is implemented by the lidar as described above.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, it is still for those skilled in the art. The technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

A laser radar launching device, including:

A laser emitting unit, the laser emitting unit is configured to output a laser whose wavelength can be hopped;

Dispersion unit, the dispersive unit is arranged downstream of the optical path of the laser emitting unit, and is configured to receive the laser, and according to the wavelength of the laser, the laser is emitted in different directions to obtain the The scanning of the laser in the first plane; and

A one-dimensional scanning unit, the one-dimensional scanning unit is arranged downstream of the optical path of the dispersive unit and receives the laser from the dispersive unit to obtain a scan of the laser in a second plane, wherein the first plane is vertical On the second plane.
The emission device of claim 1, wherein the dispersion unit comprises a grating, and the laser light with a wavelength hopping is emitted at the -1 level or the +1 level of the grating.
The transmitting device of claim 1, wherein the one-dimensional scanning unit is a one-dimensional galvanometer, a swing mirror, or a rotating mirror.
The emitting device according to any one of claims 1 to 3, wherein the laser emitting unit includes a tunable laser, and the tunable laser includes:

Excitation source, which can output excitation;

A gain unit, the gain unit is located downstream of the excitation source and receives excitation from the excitation source to generate stimulated radiation;

The first reflecting mirror and the second reflecting mirror, wherein the second reflecting mirror is a partially transmissive reflecting mirror, wherein the first reflecting mirror and the second reflecting mirror form a laser resonant cavity, and the gain unit is located in the laser In the resonant cavity, a laser oscillation of a specific wavelength is formed in the laser resonant cavity, and the laser light generated in the laser resonant cavity is emitted from the second mirror to form an outgoing laser;

FP etalon, the FP etalon is arranged in the laser resonator to adjust the wavelength of the emitted laser;

Wherein the laser resonator has multiple longitudinal modes, the FP etalon has multiple transmission peaks, and the gain unit is configured to change the longitudinal mode of the laser resonator so that one of the transmission peaks and one of the longitudinal modes It is basically matched, and the transmission peak that establishes the matching relationship can be changed, thereby changing the wavelength of the emitted laser light.
8. The transmitting device of claim 4, wherein the gain unit is configured to change the cavity length of the laser resonant cavity by changing the current injected into the gain unit, thereby changing the longitudinal mode of the laser resonant cavity.
The launching device of claim 5, wherein the laser emitting unit further comprises a control unit connected to the gain unit and injects current into the gain unit, and the control unit is configured to feed the gain unit The unit injects current to make one of the longitudinal modes of the laser cavity and one of the transmission peaks of the FP etalon basically match, and can inject different currents into the gain unit to make the FP etalon different The transmission peak is basically matched with one of the longitudinal modes, thereby changing the wavelength of the outgoing laser.
5. The transmitting device according to claim 4, wherein the FP etalon is arranged obliquely with respect to the normal of the first mirror and the second mirror.
5. The emitting device according to claim 4, wherein the laser emitting unit further comprises a tunable filter, and the tunable filter is arranged in the laser resonant cavity to adjust the wavelength range of the emitted laser light.
The emitting device according to any one of claims 1 to 3, wherein the laser emitting unit includes a plurality of lasers, and the wavelengths of the plurality of lasers are different from each other.
The emitting device according to any one of claims 1 to 3, further comprising a laser driving unit connected to the laser emitting unit and configured to drive the laser emitting unit to output sequentially in a certain time The laser whose wavelength can be hopped.
A laser radar launching device, including:

A laser emitting unit, the laser emitting unit is configured to output a laser whose wavelength can be hopped;

Dispersion unit, the dispersive unit is arranged downstream of the optical path of the laser emitting unit, and is configured to receive the laser, and according to the wavelength of the laser, the laser is emitted in different directions to obtain the The scanning of the laser in the first plane; and

A rotary drive unit configured to drive the laser emitting unit and the dispersive unit to rotate around a rotation axis to obtain a scan of the laser light from the dispersive unit in a second plane, wherein the first The plane is perpendicular to the second plane, and the rotation axis is parallel to the first plane.
11. The emitting device of claim 11, wherein the laser emitting unit comprises a tunable laser, and the tunable laser comprises:

Excitation source, which can output excitation;

A gain unit, the gain unit is located downstream of the excitation source and receives excitation from the excitation source to generate stimulated radiation;

The first reflecting mirror and the second reflecting mirror, wherein the second reflecting mirror is a partially transmissive reflecting mirror, wherein the first reflecting mirror and the second reflecting mirror form a laser resonant cavity, and the gain unit is located in the laser In the resonant cavity, a laser oscillation of a specific wavelength is formed in the laser resonant cavity, and the laser light generated in the laser resonant cavity is emitted from the second mirror to form an outgoing laser;

FP etalon, the FP etalon is arranged in the laser resonator to adjust the wavelength of the emitted laser;

Wherein the laser resonator has multiple longitudinal modes, the FP etalon has multiple transmission peaks, and the gain unit is configured to change the longitudinal mode of the laser resonator so that one of the transmission peaks and one of the longitudinal modes It is basically matched, and the transmission peak that establishes the matching relationship can be changed, thereby changing the wavelength of the emitted laser light.
The transmitting device of claim 12, wherein the gain unit is configured to change the length of the laser resonant cavity by changing the current injected into the gain unit, thereby changing the longitudinal mode of the laser resonant cavity.
The launching device according to claim 13, wherein the laser emitting unit further comprises a control unit connected to the gain unit and injects current into the gain unit, and the control unit is configured to send current to the gain unit. The unit injects current to make one of the longitudinal modes of the laser cavity and one of the transmission peaks of the FP etalon basically match, and can inject different currents into the gain unit to make the FP etalon different The transmission peak is basically matched with one of the longitudinal modes, thereby changing the wavelength of the outgoing laser.
The transmitting device according to claim 12, wherein the FP etalon is arranged obliquely with respect to the normals of the first mirror and the second mirror, wherein the laser emitting unit further includes a tunable filter, The tunable filter is arranged in the laser resonant cavity to adjust the wavelength range of the emitted laser light.
A type of lidar, including:

The launching device according to any one of claims 1-15, the launching device is configured to emit a detection laser for detecting a target;

A receiving unit, the receiving unit includes a photodetector configured to receive the echo of the detection laser diffusely reflected on the target, and convert it into an electrical signal;

A signal processing unit, which is coupled to the receiving unit, and generates a laser radar point cloud according to the electrical signal.
The lidar according to claim 16, wherein the receiving unit further comprises a receiving lens and an optical fiber, one end surface of the optical fiber is located at the focal plane of the receiving lens, and the receiving lens condenses the echo to the The one end face of the optical fiber is coupled into the optical fiber, and the echo is emitted through the other end face of the optical fiber and received by the photodetector.
A detection method of lidar includes:

Drive a laser emitting unit to output a laser whose wavelength can be hopped;

Receiving the laser light by a dispersion unit, and emitting the laser light in different directions according to different wavelengths of the laser light, so as to obtain the scanning of the laser light in the first plane;

Receiving the laser light from the dispersion unit through a one-dimensional scanning unit arranged downstream of the optical path of the dispersion unit to obtain a scan of the laser light in a second plane, wherein the first plane is perpendicular to the second plane; with

The echo reflected by the laser on the target is received by a photodetector and converted into an electrical signal.
A detection method of lidar includes:

Drive a laser emitting unit to output a laser whose wavelength can be hopped;

Receiving the laser light by a dispersion unit, and making the laser light emit in different directions in the first plane according to the wavelength of the laser light, so as to obtain the scanning of the laser light in the first plane;

The laser emitting unit and the dispersion unit are driven to rotate around a rotation axis to obtain a scan of the laser light from the dispersion unit in a second plane, wherein the first plane is perpendicular to the second plane, and the rotation The axis is parallel to the first plane; and

The echo reflected by the laser on the target is received by a photodetector and converted into an electrical signal.
A tunable laser, including:

Excitation source, which can output excitation;

A gain unit, the gain unit is located downstream of the excitation source and receives excitation from the excitation source to generate stimulated radiation;

The first reflecting mirror and the second reflecting mirror, wherein the second reflecting mirror is a partially transmissive reflecting mirror, wherein the first reflecting mirror and the second reflecting mirror form a laser resonant cavity, and the gain unit is located in the laser In the resonant cavity, a laser oscillation of a specific wavelength is formed in the laser resonant cavity, and the laser light generated in the laser resonant cavity is emitted from the second mirror to form an outgoing laser;

FP etalon, the FP etalon is arranged in the laser resonator to adjust the wavelength of the emitted laser,

Wherein the laser resonator has multiple longitudinal modes, the FP etalon has multiple transmission peaks, and the gain unit is configured to change the longitudinal mode of the laser resonator so that one of the transmission peaks and one of the longitudinal modes It is basically matched, and the transmission peak that establishes the matching relationship can be changed, thereby changing the wavelength of the emitted laser light.
The tunable laser according to claim 20, wherein the gain unit is configured to change the cavity length of the laser resonator by changing the current injected into the gain unit, thereby changing the longitudinal mode of the laser resonator.
The tunable laser of claim 21, further comprising a control unit connected to the gain unit and injecting current into the gain unit, the control unit being configured to inject current into the gain unit so that One of the longitudinal modes of the laser resonator is basically matched with one of the transmission peaks of the FP etalon, and different currents can be injected into the gain unit to make the different transmission peaks of the FP etalon match one of the transmission peaks. The longitudinal modes are basically matched, thereby changing the wavelength of the outgoing laser.
The tunable laser according to any one of claims 20-22, wherein the FP etalon is arranged obliquely with respect to the normal of the first mirror and the second mirror.
22. The tunable laser according to any one of claims 20-22, further comprising a tunable filter which is arranged in the laser resonator to adjust the wavelength range of the emitted laser light.
The tunable laser according to any one of claims 20-22, wherein the excitation source includes a pump unit that can generate pump light or pump current, and the tunable laser further includes The collimating lens between the FP etalon and the FP etalon is used to collimate the light beam emitted from the gain unit and then enter the FP etalon.
A control method of a tunable laser includes:

Generate incentives through incentive sources;

The excitation is received by a gain unit to generate stimulated radiation, wherein the gain unit is located in a laser resonant cavity, the laser resonant cavity includes a first mirror and a second mirror, and the second mirror is partially transmissive The reflector, forming a laser oscillation of a specific wavelength in the laser resonant cavity, and the laser generated in the laser resonant cavity is emitted from the second reflector; wherein the laser resonant cavity has multiple longitudinal modes, the An FP etalon is arranged in the laser resonant cavity, and the FP etalon has a plurality of transmission peaks;

Changing the longitudinal mode of the laser resonant cavity by the gain unit, so that one of the transmission peaks is substantially matched with one of the longitudinal modes;

The transmission peak that establishes the matching relationship is changed by the gain unit, and the wavelength of the emitted laser light is changed.
The control method according to claim 26, wherein the step of changing the longitudinal mode of the laser resonant cavity comprises: changing the current injected into the gain unit to change the cavity length of the laser resonant cavity, thereby changing the laser resonant cavity The longitudinal mode.
26. The control method according to claim 26, wherein the step of changing the transmission peak that establishes the matching relationship through the gain unit to change the wavelength of the emitted laser comprises: injecting different currents into the gain unit to make the FP etalon Different transmission peaks are basically matched with one of the longitudinal modes, thereby changing the wavelength of the outgoing laser.
The control method according to any one of claims 26-28, further comprising adjusting the wavelength range of the emitted laser light through a tunable filter arranged in the laser resonator.
The control method according to any one of claims 26-28, wherein the excitation source comprises a pump unit that can generate pump light or pump current, and the laser resonant cavity is also provided with the gain unit The collimating lens between the FP etalon and the FP etalon is used to collimate the light beam emitted from the gain unit and then enter the FP etalon.
A type of lidar, including:

A transmitting unit, the transmitting unit comprising the tunable laser according to claims 20-25, configured to emit a detection laser beam for detecting a target;

A receiving unit, the receiving unit is configured to receive the echo of the detection laser beam reflected on the target, and convert it into an electrical signal;

A processing unit, which is coupled to the receiving unit, and calculates the distance between the target and the lidar according to the electrical signal.