CN217639518U - Coherent detection device, optical prism and coherent speed measurement system - Google Patents

Abstract

The disclosure provides a coherent detection device, an optical prism and a coherent speed measurement system, wherein the coherent detection device comprises a laser source, the optical prism, a beat frequency element and a photoelectric detector. The laser source is used for emitting laser; the optical prism is configured to refract the laser light into a plurality of laser beam split beams projected toward the target object and receive signal light reflected or scattered back from the target object by the plurality of laser beam split beams; the beat frequency element is configured to carry out coherent beat frequency on the signal light and the local oscillation light of the laser to generate beat frequency light; the optical prism has a simple structure, realizes the structural simplification of a coherent detection device, is beneficial to improving the stability of the device, is convenient to maintain, and effectively reduces the cost.

Description

Coherent detection device, optical prism and coherent speed measurement system

Technical Field

The present disclosure relates to the field of optical coherence technology, and more particularly to a coherent detection device; the disclosure also relates to an optical prism applied to the coherent detection device and a coherent speed measurement system comprising the coherent detection device.

Background

In a coherent speed measurement system, a laser source emits laser to a target, the emitted laser is deflected by an optical scanning device, the target is scanned and detected, signal light reflected or scattered from a target object is received, and angle and position information is fed back in real time in the scanning process. The received signal is compared with the transmitted detection signal, and after proper processing, the relevant information of the target, such as the parameters of target distance, direction, height, speed, attitude, even shape and the like, can be obtained, thereby detecting, tracking and identifying the target.

The optical scanning device is an important component of the laser radar, and the current optical scanning devices mainly include the following two types: in the first device, two groups of mirrors are used to transmit and receive signals, and referring to fig. 1, the two groups of mirrors rotate in a mode of forming a certain cone angle with each other through a rotating part to realize optical scanning; in the second device, a wedge-shaped optical prism is used to transmit and receive signals, and referring to fig. 2, the optical prism is driven to rotate by a rotating component to realize optical scanning.

Both the two optical scanning devices need to be driven to rotate by the rotating part, the rotating part is complex and heavy in structure, high in cost, poor in long-term working stability and required to be maintained regularly, and challenges and adverse factors are brought to the miniaturization and the stability of the system.

SUMMERY OF THE UTILITY MODEL

The disclosure provides a coherent detection device, an optical prism and a coherent speed measurement system for solving the problems in the prior art.

According to a first aspect of the present disclosure, there is provided a coherent detection device comprising:

a laser source for emitting laser light;

an optical prism configured to refract the laser light into a plurality of laser beam split beams projected toward an object and receive signal light reflected or scattered back from the object by the plurality of laser beam split beams;

a beat frequency element configured to coherently beat frequency the signal light and a local oscillation light of the laser light to generate beat frequency light;

a photodetector for converting the beat frequency light received into an electrical signal.

In one embodiment of the present disclosure, the optical prism includes an incident surface for receiving the laser light, and a plurality of refraction surfaces for refracting out the laser beam split, the plurality of refraction surfaces being respectively inclined with respect to the incident surface.

In one embodiment of the disclosure, the plurality of refraction surfaces are configured to receive and refract the signal light so that the signal light is reversely emitted from the incidence surface along the path of the laser light.

In one embodiment of the present disclosure, the plurality of refractive surfaces are inclined in different directions with respect to the incident surface.

In one embodiment of the present disclosure, the inclination angle α between the plurality of refractive surfaces and the incident surface is set at 5 ° to 12 °.

In one embodiment of the present disclosure, included angles β formed between the plurality of laser beam splitters and the laser light, respectively, are set at 10 ° to 35 °.

In one embodiment of the present disclosure, the refractive index n1 of the optical prism is set between 1.45 and 4.

In one embodiment of the present disclosure, the plurality of refractive surfaces are uniformly distributed in a circumferential direction of the optical prism end surface.

In one embodiment of the present disclosure, the plurality of the refraction surfaces are gradually inclined toward the incident surface from the edge to the center of the optical prism.

In one embodiment of the present disclosure, the plurality of refraction surfaces are identical in shape and area.

In one embodiment of the present disclosure, a plurality of the refraction surfaces are each provided in a fan-shaped structure, and the refraction surfaces are provided in four and constitute a cone-shaped structure.

In an embodiment of the present disclosure, the optical system further includes a collimating element configured to collimate the laser light emitted by the laser light source and emit the collimated laser light to the optical prism, and to emit the signal light received by the optical prism to the beat frequency element.

According to the second aspect of the present disclosure, there is also provided an optical prism, including an incident surface for receiving laser light, and a plurality of refraction surfaces for refracting out laser beam splitting, the plurality of refraction surfaces forming inclination angles with the incident surface, respectively;

the refraction surface is configured to project the laser beams toward an object, and receive and refract the signal light reflected or scattered from the object by the laser beams, so that the signal light is reversely emitted from the incidence surface along the path of the laser beams.

According to a third aspect of the present disclosure, there is also provided a coherent tachometry system, including the coherent detection apparatus in the above embodiments.

In one embodiment of the present disclosure, the coherent velocity measurement system is a doppler wind lidar.

The coherent detection device has the advantages that the coherent detection device refracts laser beams out of a plurality of laser beam splitting beams projected to the target object through the optical prism and receives signal light reflected or scattered back by the target object, compared with the mode that the conventional optical scanning device carries out optical scanning through rotation, a rotating part is omitted, the structure of the coherent detection device is simplified, the stability of the device is improved, the device is convenient to maintain, and the cost is effectively reduced.

Other features of the present disclosure and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.

FIG. 1 is a background art schematic of the present disclosure;

FIG. 2 is a background art schematic of the present disclosure;

fig. 3 is a schematic overall structure diagram of a coherent detection apparatus provided in an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of an optical prism refracting laser light provided by an embodiment of the present disclosure;

fig. 5 is a schematic diagram of an optical prism provided in an embodiment of the present disclosure receiving signal light;

FIG. 6 is a schematic structural diagram of an optical prism provided in an embodiment of the present disclosure;

FIG. 7 is a front view of an optical prism provided by one embodiment of the present disclosure as including four refracting surfaces;

FIG. 8 is a front view of an optical prism provided by one embodiment of the present disclosure as including three refracting surfaces;

FIG. 9 is a front view of an optical prism provided by one embodiment of the present disclosure as including five refracting surfaces;

fig. 10 is a schematic structural diagram of a doppler wind lidar according to an embodiment of the present disclosure. The one-to-one correspondence between component names and reference numbers in fig. 1 to 10 is as follows:

1. a laser source; 2. a collimating element; 3. an optical prism; 31. an incident surface; 32. a refracting surface; 4. a beat element; 5. a photodetector.

Detailed Description

Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In this document, "upper", "lower", "front", "rear", "left", "right", and the like are used only to indicate relative positional relationships between relevant portions, and do not limit absolute positions of the relevant portions.

In this document, "first", "second", and the like are used only for distinguishing one from another, and do not indicate the degree and order of importance, the premise that each other exists, and the like.

In this context, "equal", "same", etc. are not strictly mathematical and/or geometric limitations, but also include tolerances as would be understood by a person skilled in the art and allowed for manufacturing or use, etc.

Unless otherwise indicated, numerical ranges herein include not only the entire range within its two endpoints, but also several sub-ranges subsumed therein.

The present disclosure provides a coherent detection device comprising a laser source, an optical prism, a beat frequency element, and an optical detector. The optical prism is configured to refract the laser light into a plurality of laser beam splits that are projected to an object, and to receive signal light that is reflected or scattered back from the object by the plurality of laser beam splits. The beat frequency element is configured to perform beat frequency coherence on the signal light and local oscillation light of the laser to generate beat frequency light, and the photoelectric detector is used for receiving the beat frequency light and converting the beat frequency light into an electric signal. The target distance, direction, height, speed, posture, even shape and other related information of the target object can be further obtained through the electric signals, so that the target can be detected, tracked and identified.

The optical prism refracts one laser beam into a plurality of laser beams through the structural arrangement to split the beams and detect the target object so as to acquire the related information of the target object. The optical prism has a simple structure, realizes the structural simplification of the coherent detection device, is favorable for improving the stability of the device, is convenient to maintain and effectively reduces the cost.

The technical solution of the present disclosure will be described in detail with reference to specific structures.

In some embodiments of the present disclosure, as shown in fig. 3, the coherent detection device includes a laser source 1 and an optical prism 3, the laser source 1 is configured to emit laser light, the optical prism 3 receives the laser light and refracts one laser light into a plurality of laser beam splits, and the plurality of laser beam splits are projected to an object to be detected by the optical prism 3. The multiple laser beams are split to reach the target object and then reflected or scattered back to the signal light, and the optical prism 3 receives the returned signal light.

The laser light received by the optical prism 3 is a collimated laser beam, and as shown in fig. 3, in a specific embodiment, a collimating element 2 is disposed between the laser light source 1 and the optical prism 3, and the collimating element 2 receives the laser light emitted by the laser light source 1, collimates the laser light, and emits the laser light to the optical prism 3. The collimating element 2 is also able to receive the optical signal back to the optical prism 3. The collimating element 2 may be a collimating optical telescope or other instrument capable of collimating the laser light.

The coherent detection device further comprises a beat frequency element 4 and a photoelectric detector 5, wherein the laser source 1 emits local oscillator light of laser to the beat frequency element 4, the collimating element 2 emits received signal light to the beat frequency element 4, and the local oscillator light and the signal light can carry out beat frequency coherence in the beat frequency element 4 to generate beat frequency light. The beat frequency component 4 transmits beat frequency light to the photodetector 5, and the photodetector 5 converts the beat frequency light into an electric signal. The beat frequency element 4 may be a light mixer, a fiber coupler, or an optical element thereof capable of realizing beat frequency coherence. The electric signal obtained by the photodetector 5 can be further sent to an analog-to-digital converter for signal conversion, and finally the distance, direction, speed and other information of the target object can be obtained.

In some embodiments of the present disclosure, the coherent detection device further comprises a fiber optic circulator. The optical fiber circulator is connected with the laser source 1 through the first end, receives laser, transmits the laser to the optical prism 3 through the second end, the beat frequency element 4 is the terminal surface arranged at the second end of the optical fiber circulator, the terminal surface receives the signal light returning to the optical prism 3, and reflects the local oscillator light of the laser, the signal light and the local oscillator light can carry out coherent beat frequency on the terminal surface, beat frequency light is generated, and the beat frequency light is output to the photoelectric detector 5 through the third end of the optical fiber circulator.

The coherent detection device is applied to the laser radar and can be used in the fields of atmospheric environment monitoring, aircraft tracking identification, geographic information acquisition and the like. Taking the example of detecting an atmospheric wind field, the present disclosure describes the principle of coherent detection devices in detail below.

When a laser signal with the frequency v is emitted into the atmosphere and irradiates aerosol molecules in the air, scattering occurs and an echo is generated, the frequency of the laser signal can shift, and the frequency v of the echo signal _x Expressed as:

where u represents the velocity of particle movement in the aerosol, i.e. the wind velocity, θ _x Representing the angle between the wind direction and the propagation direction of the emitted laser signal, and lambda represents the laser wavelength.

The echo signal is received by a detector, the frequency v of the laser signal being received _r Expressed as:

wherein, theta _r Representing the angle between the wind direction and the direction of propagation of the received laser signal.

The frequency v of the received laser signal _r With the frequency v of the emitted laser signal _x By subtracting, the drift (called Doppler shift) v of the laser signal frequency can be obtained _d ：

In general, the laser signal transmission and reception directions coincide, i.e. θ _x ＝θ _r Thus:

wherein u is _r Indicating the magnitude of the wind speed in the direction of measurement. It can be seen that by measuring the frequency difference between the received signal and the transmitted signal, the wind speed in the measuring direction (radial wind speed) can be obtained.

In some embodiments of the present disclosure, as shown in fig. 4, the optical prism 3 includes an incident surface 31 for receiving the laser light, and a plurality of refraction surfaces 32 for refracting the laser beam split, the plurality of refraction surfaces 32 being respectively inclined with respect to the incident surface 31, the plurality of laser beam split being at an angle with the laser light received by the incident surface 31. In detail, the incident surface 31 and the refraction surface 32 are distributed on opposite sides of the optical prism 3, the direction of the laser light is perpendicular to the incident surface 31, and each refraction surface 32 refracts one laser beam split. The optical prism 3 includes at least three refraction surfaces 32, and refracts at least three laser beam splits to acquire information of position, distance, size, etc. of the target object.

As shown in fig. 5, the plurality of refraction surfaces 31 of the optical prism 3 also receive the signal light returning from the object and refract the signal light so that the signal light is reversely emitted from the incidence surface 31 along the path of the laser light.

In some embodiments of the present disclosure, as shown in fig. 6, the plurality of refraction surfaces 32 of the optical prism 3 are inclined in different directions with respect to the incident surface 31, so that the plurality of laser beams can be emitted in different directions to detect the target object at different positions. In detail, the plurality of refraction surfaces 32 may be inclined in different directions by the same angle, or may be inclined in different directions by different angles. The specific inclination angles of the plurality of refraction surfaces 32 can be selected according to the position, distance, size and other factors of different targets.

According to the law of refraction, light rays incident on interfaces of different media are reflected and refracted. The incident light and the refracted light are positioned on the same plane, and the included angle between the incident light and the normal line of the interface satisfies the following relation:

n ₁ sinθ ₁ ＝n ₂ sinθ ₂ (2.1)

wherein n is ₁ Is the refractive index of the medium on the incident light side, n ₂ Is the refractive index of the medium on the side of the outgoing light, theta ₁ Is the angle between the incident light and the interface normal, θ ₂ Is the angle between the outgoing light and the interface normal.

In the present disclosure, as shown in fig. 4, the inclination angle between the plurality of refraction surfaces 32 of the optical prism 3 and the incident surface 31 is α, and the included angle formed between the refracted laser beam and the incident laser beam is β. Since the direction of the laser light is perpendicular to the incident surface 31, the angle of the laser light passing through the incident surface 31 is not deflected, and the angle between the laser light and the normal of the refraction surface 32 is equal to the inclination angle α between the refraction surface 32 and the incident surface 31. The angle between the laser beam split and the normal to refractive surface 32 is α + β. The laser angle, the laser beam splitting angle and the refraction surface 32 angle satisfy the following conditions:

n ₁ sinα＝n ₂ sin(α+β) (2.2)

wherein the refractive index of the optical prism 3 is n ₁ The refractive index of air is n ₂ 。

In some embodiments of the present disclosure, the inclination angle α between the plurality of refraction surfaces 32 and the incident surface 31 may be set between 5 ° and 12 °, and the plurality of laser beams are split to be projected to particles in the atmosphere for detecting the wind speed. The included angles beta formed between the plurality of laser beam splitting parts and the laser can be set to be 10-35 degrees. Refractive index n of optical prism 3 ₁ May be set between 1.45 and 4. For example, the inclination angle α between the plurality of refraction surfaces 32 and the incident surface 31 is set to 10 °, and the refractive index n of the optical prism 3 is set to ₁ Set to 1.2, the refractive index of air is n ₂ Generally 1, the angle β between the laser beam split and the incident laser can be calculated based on the above equation (2.2).

The optical prism 3 is made of all optical materials capable of realizing laser (wavelength 200nm to 2200 nm) deflection, including but not limited to fused silica glass, K9 glass, silicon and other optical materials. The optical prism 3 is composed of a plurality of regions between the refraction surfaces 32 and the incidence surface 31, the optical prism 3 may be an integrated structure, or may be formed by splicing a plurality of regions, and the plurality of regions of the optical prism 3 may be made of optical materials with different refractive indexes, which is not limited in the present disclosure.

In some embodiments of the present disclosure, as shown in fig. 6, the plurality of refractive surfaces 32 of the optical prism 3 may be uniformly distributed in the circumferential direction of the end surface of the optical prism 3, so that the plurality of laser beams are split to be emitted in a ring-shaped manner. The plurality of refractive surfaces 32 may be configured to have the same shape and area to enable uniform distribution of the plurality of laser beam splits. The plurality of refraction surfaces 32 may be inclined gradually toward the incident surface 31 from the edge to the center of the optical prism 3, and may be configured in a concave structure so that the plurality of laser beams can be emitted in a divergent state.

In one embodiment of the present disclosure, as shown in fig. 6 and 7, the plurality of refractive surfaces 32 of the optical prism 3 are each provided in a fan-shaped structure, and the refractive surfaces 32 are provided in four, and constitute a tapered structure. The diameter of the optical prism 3 is set to be 50 mm or more. Referring to the view of fig. 7, four fan-shaped refraction surfaces 32 are uniformly distributed on the optical prism 3 at 90 ° to each other, and four laser beam splitting is also distributed at 90 ° to each other. As shown in fig. 6, when one laser beam a enters the optical prism 3 from the incident surface 31, the four refraction surfaces 32 split the incident laser beam a into four laser beams A1, A2, A3, and A4.

In one embodiment of the present disclosure, as shown in fig. 8, the optical prism 3 includes three fan-shaped refracting surfaces 32, and the refracting surfaces 32 constitute a tapered structure. Three fan-shaped refraction surfaces 32 are uniformly distributed on the optical prism 3 and mutually form an angle of 120 degrees, and three laser beam splitting are also mutually distributed in an angle of 120 degrees. When a laser beam B enters the optical prism 3 from the incident surface 31, the four refraction surfaces 32 split the incident laser beam B into three laser beam splits B1, B2, and B3.

In one embodiment of the present disclosure, as shown in fig. 9, the optical prism 3 includes five fan-shaped refracting surfaces 32, and constitutes a tapered structure. Five fan-shaped refraction surfaces 32 are uniformly distributed on the optical prism 3 and mutually form 72 degrees, and three laser beam splitting are also mutually formed 72 degrees. When a laser beam C enters the optical prism 3 from the incident surface 31, the five refraction surfaces 32 divide the incident laser beam C into five laser beam splits C1, C2, C3, C4 and C5.

The disclosure also provides an optical prism, which can be applied to an optical scanning device of a laser radar. The optical prism includes an incident surface 31 for receiving the laser light, and a plurality of refraction surfaces 32 for refracting the laser light beam split, the plurality of refraction surfaces 32 forming inclination angles with the incident surface 31, respectively. The refraction surface 32 is configured to project the plurality of laser beams toward the object, and to receive and refract the signal light reflected or scattered from the object by the plurality of laser beams, so that the signal light is reversely emitted from the incident surface 31 along the path of the laser beam. The specific structure and principle of the optical prism are consistent with those of the coherent detection device disclosed in the present disclosure, and the detailed description of the present disclosure is omitted here.

The present disclosure further provides a coherent speed measurement system, which includes a coherent detection device, and the specific structure and principle of the coherent detection device are consistent with the above coherent detection device of the present disclosure, which is not described herein again. The coherent speed measurement system further includes a control and data processing subsystem, a temperature control auxiliary subsystem, etc. known to those skilled in the art.

In an embodiment of the present disclosure, the coherent velocity measurement system is a doppler wind lidar, which can invert wind profile information in atmospheric space, and provide key data support for application fields such as weather, environmental protection, or airport runways. Compared with the existing laser radar, the coherent speed measurement system disclosed by the invention adopts the optical prism with a simple structure to perform optical scanning on the target object, and does not need a rotating part to drive the optical element to perform rotating scanning, so that the hardware cost is reduced, the maintenance is convenient, and the service life of the whole system is prolonged.

In one embodiment of the present disclosure, the doppler wind lidar employs the following scheme for signal detection. As shown in fig. 10, the doppler wind lidar includes a laser source 1, a fiber circulator, a collimating element 2, an optical prism 3, a fiber mixer or a fiber coupler, a photodetector 5, and an analog-to-digital converter. The optical fiber circulator comprises a port 1, a port 2 and a port 3 which are different in direction, wherein the port 1 is connected with the laser source, the port 2 is connected with the collimating element 2, and the port 3 is connected with the optical fiber mixer or the optical fiber coupler. Laser emitted by a laser source is transmitted to a port 2 through a port 1 of an optical fiber circulator, then is transmitted to a collimating element 2 through the port 2 of the optical fiber circulator, and then is transmitted to an optical prism 3 from the collimating element 2, so that the refraction of the laser and the reception of signal light are completed, the signal light received by the collimating element 2 is transmitted to the port 3 through the port 2 of the optical fiber circulator and is output, the local oscillator light output by the laser source and the signal light output by the port 3 of the optical fiber circulator are transmitted to an optical fiber mixer or an optical fiber coupler, the Doppler coherence of the signal light and the local oscillator light is completed, beat frequency light is generated, then the beat frequency light is converted into an electric signal by a photoelectric detector 5, finally the electric signal is transmitted to an analog-to-digital converter, the signal acquisition is completed, and finally Doppler signals, the information such as Doppler speed and the like are reflected.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. The scope of the present disclosure is defined by the appended claims.

Claims (15)

1. A coherent detection device, comprising:

a laser source (1), the laser source (1) being configured to emit laser light;

an optical prism (3), the optical prism (3) being configured to refract the laser light into a plurality of laser beam split beams projected toward an object and receive signal light reflected or scattered back from the object by the plurality of laser beam split beams;

a beat frequency element (4), the beat frequency element (4) being configured to coherently beat frequency the signal light and the local oscillation light of the laser light to generate beat frequency light;

a photodetector (5), said photodetector (5) being adapted to receive said beat frequency light and convert it into an electrical signal.

2. The coherent detection device according to claim 1, wherein the optical prism (3) comprises an incident surface (31) for receiving the laser light, and a plurality of refraction surfaces (32) for refracting the laser light beam split, the plurality of refraction surfaces (32) being respectively inclined with respect to the incident surface (31).

3. The coherent detection device of claim 2, wherein a plurality of the refraction surfaces (32) are configured to receive and refract the signal light such that the signal light is reversely emitted from the incidence surface (31) along the path of the laser light.

4. The coherent detection device according to claim 2, wherein the plurality of refraction surfaces (32) are inclined in different directions with respect to the incident surface (31).

5. A coherent detection device according to claim 3, wherein the angle of inclination a between the plurality of refractive surfaces (32) and the entrance surface (31) is set between 5 ° and 12 °.

6. The coherent detection device of claim 2, wherein the included angles β formed between the plurality of laser beam splitters and the laser light are set to 10 ° to 35 °.

7. The coherent detection device according to claim 2, characterized in that the refractive index n1 of the optical prism (3) is set between 1.45 and 4.

8. The coherent detection device according to claim 2, wherein a plurality of the refraction surfaces (32) are uniformly distributed in a circumferential direction of the end face of the optical prism (3).

9. The coherent detection device according to claim 2, wherein the plurality of refraction surfaces (32) are gradually inclined from the edge to the center of the optical prism (3) toward the incident surface (31).

10. The coherent detection device according to claim 2, wherein the plurality of refraction surfaces (32) are identical in shape and area.

11. The coherent detection device according to claim 10, wherein a plurality of the refraction surfaces (32) are arranged in a fan-shaped configuration, and the refraction surfaces (32) are arranged in four and form a cone-shaped configuration.

12. The coherent detection device according to any one of claims 1 to 11, further comprising a collimating element (2), wherein the collimating element (2) is configured to collimate the laser light emitted from the laser source (1) and emit the collimated laser light to the optical prism (3), and to emit the signal light received by the optical prism (3) to the beat frequency element (4).

13. An optical prism, characterized by comprising an incident surface (31) for receiving laser light, and a plurality of refraction surfaces (32) for refracting laser light split, wherein the plurality of refraction surfaces (32) respectively form an inclination angle with the incident surface (31);

the refraction surface (32) is configured to project the plurality of laser beams toward an object, and receive and refract the signal light reflected or scattered back from the object by the plurality of laser beams, so that the signal light is emitted in a reverse direction from the incidence surface (31) along a path of the laser beams.

14. A coherent pacing system comprising a coherent detection apparatus according to any one of claims 1 to 12.

15. The coherent velocity measurement system according to claim 14, wherein the coherent velocity measurement system is a doppler wind lidar.

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