Lidar

Abstract

The application is suitable for the technical field of laser radar, and provides a laser radar, which comprises a light source, a transmitting module, a receiving module, a transmission module, a detecting module and a signal processing module; the transmission module comprises a first coupler and a plurality of transmission media, wherein the local oscillator beam is transmitted to at least one transmission medium for delay processing through the first coupler, and the delay amount of the at least one transmission medium is different from that of the other transmission media; the detecting module is connected with the transmission module and the receiving module respectively, is used for receiving the echo signal and the delayed local oscillator beam output by the transmission module, performing beat frequency processing on the echo signal and the delayed local oscillator beam to obtain a beat frequency signal, and converting the beat frequency signal into a detecting electric signal; and the signal processing module is electrically connected with the detecting module, is used for determining a to-be-measured object according to the detecting electric signal. The laser radar provided by the application can improve the strength of the detection signal in long-distance measurement.

Description

Technical Field

[0001] This invention belongs to the field of lidar technology, and particularly relates to a lidar system. Background Technology

[0002] Frequency Modulated Continuous Wave (FMCW) lidar utilizes the principle of coherent detection for measurement. During measurement, the lidar provides a probe beam and a local oscillator beam. The probe beam is reflected by the target to form an echo signal. The lidar receives the echo signal and beats it with the local oscillator beam to obtain the beat frequency signal. The parameters of the target are then derived by analyzing the beat frequency signal.

[0003] Due to the coherence of lasers and the coherent detection principle of lidar, the signal strength detected by lidar is directly related to the time difference between the echo signal and the local oscillator beam. However, when measuring long distances, the number of effective sampling points acquired by lidar is relatively small, resulting in a weaker detected signal and affecting the detection quality. Summary of the Invention

[0004] The purpose of this invention is to provide a lidar that addresses the technical problem of weak detection signal strength when measuring long distances in the prior art.

[0005] This invention is implemented as follows: a lidar includes a light source for providing a laser beam and dividing the laser beam into a local oscillator beam and a detection beam; a transmitting module for receiving the detection beam and transmitting the detection beam into a detection space; a receiving module for receiving an echo signal, wherein the echo signal is the beam of the detection beam reflected by a target object in the detection space; a transmission module including a first coupler and multiple transmission media, wherein the local oscillator beam is transmitted to at least one of the transmission media for delay processing through the first coupler, wherein the delay amount of at least one of the transmission media is different from the delay amounts of the other transmission media; a detection module connected to the transmission module and the receiving module respectively, for receiving the echo signal and the delayed local oscillator beam output by the transmission module, performing beat frequency processing on the echo signal and the delayed local oscillator beam to obtain a beat frequency signal, and converting the beat frequency signal into a detection electrical signal; and a signal processing module electrically connected to the detection module for determining the target object based on the detection electrical signal.

[0006] In some embodiments, the delay amounts of each of the transmission media are different.

[0007] In some embodiments, the transmission medium is provided with n, where n is greater than or equal to 2, and each of the n-1 transmission media is provided with a delay line. When n-1 is greater than or equal to 2, the length of each delay line is different.

[0008] In some embodiments, the materials of all the transmission media are the same.

[0009] In some embodiments, the delay line is an optical fiber or an optical waveguide.

[0010] In some embodiments, the first coupler is a first beam splitter or a first optical switch.

[0011] In some embodiments, the first coupler includes a first beam splitter for splitting the local oscillator beam into multiple beams, and the transmission medium is used to transmit the split beams.

[0012] In some embodiments, the transmission module further includes a second coupler having multiple receiving ends and an output end, wherein the receiving ends are connected to the transmission medium in a one-to-one correspondence, and the second coupler is used to receive the delayed local oscillator beam and provide it to the detection module.

[0013] In some embodiments, the second coupler is a first beam combiner or a second optical switch.

[0014] In some embodiments, the receiving module includes multiple receiving units, the detection module includes multiple detection units, and the transmission medium, the receiving unit, and the detection unit correspond one-to-one; the detection unit receives the delayed local oscillator beam provided by the transmission medium and the echo signal provided by the receiving unit and performs beat frequency to obtain the beat frequency signal, and converts the beat frequency signal into the detection electrical signal.

[0015] In some embodiments, the detection unit includes a first beam combiner and a balanced detector. The first beam combiner is used to receive the echo signal and the delayed local oscillator beam output by the transmission module, and to perform beat frequency processing on the echo signal and the delayed local oscillator beam to obtain the beat frequency signal. The balanced detector is used to convert the beat frequency signal into the detection electrical signal.

[0016] The technical advantages of this invention compared to existing technologies are as follows: In the related technologies using the lidar provided in this application embodiment, at long interference distances, the long signal propagation time results in fewer effective signal points received within the same sampling time, thus reducing the number of effective points in the Fast Fourier Transform (FFT) and lowering the signal resolution and signal-to-noise ratio. However, the lidar provided in this application embodiment uses multiple transmission media in the transmission module, with at least one transmission medium having a different delay than the others. Compared to using only one transmission medium without delay, this allows the local oscillator beam to be divided into multiple signals with different delays. Firstly, at long distances, the delay of the local oscillator beam reduces the optical path difference between the echo signal and the local oscillator beam. According to the principle of FMCW lidar, this reduces the frequency of the beat frequency signal, increases the number of effective interference points (i.e., the number of effective FFT points), and thus improves the intensity of the ranging signal at long distances. Secondly, the optical path incorporates multiple local oscillator optical paths with different delay values. Simultaneous operation allows for signal processing and superposition at the signal end, thereby improving signal strength. Thirdly, the frequency of the beat frequency signal is positively correlated with the ranging distance. At long ranging distances, this increases the pressure on the bandwidth of the acquisition card and the balanced detector. Adding a delay to the local oscillator reduces the frequency of the beat frequency signal, thus reducing the requirements on the acquisition card and the balanced detector. Fourthly, adding a delay to the local oscillator can shift the frequency of near-range ranging to a higher frequency. This avoids the negative frequency flipping problem even at high speeds near the near end, thus solving the negative frequency flipping problem caused by high speeds near the near end and ensuring the correctness and stability of the signal. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram illustrating the working principle of a frequency modulated continuous wave lidar.

[0019] Figure 2 This is a schematic diagram of the structure of a lidar provided in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the structure of a lidar provided in another embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of the structure of a lidar provided in another embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures:

[0023] 10. Light source; 11. Laser; 12. Beam splitter; 20. Transmitting module; 30. Receiving module; 31. Receiving unit; 40. Transmission module; 41. First coupler; 411. First beam splitter; 412. First optical switch; 42. Transmission medium; 43. Second coupler; 50. Detection module; 51. Second beam combiner; 52. Balanced detector. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] In frequency-modulated continuous wave (FMCW) lidar, the frequency-modulated signal can be divided into two phases: the rising edge and the falling edge. For example... Figure 1 As shown, Figure 1 Figure (a) shows a schematic diagram of the FMCW lidar signal. In this figure, the solid broken line represents the frequency change of the transmitted signal over time, and the dashed broken line represents the frequency change of the received echo signal over time. Due to the target's distance and velocity, the echo signal has a time delay (τ) and a frequency shift (Δf1, Δf2). The FMCW lidar infers the target's distance and velocity by comparing the frequency difference between the transmitted and echo signals. Figure 1 Figure (b) is a schematic diagram of the beat frequency output signal. The solid broken line in the figure represents the frequency fΣ of the beat frequency signal formed after the beat frequency is applied. It is the frequency difference between the transmitted signal and the echo signal. This difference frequency signal contains information about the target distance and velocity, where f(R) represents the frequency component caused by the target distance, and 2f D This indicates the Doppler shift caused by the target velocity.

[0030] Figure 1 The broken lines in the graph follow a certain pattern of change. Specifically, during the rising edge phase, the frequency increases linearly with time, and the transmitted signal during this phase follows Formula 1:

[0031] fe(t) = f0 + αt;

[0032] The echo signal follows Formula 2:

[0033] fr(t)=f0-f D +α(t-τ);

[0034] in:

[0035]

[0036] Beat frequency signals follow Formula 3:

[0037] Δf1=ατ+f D .

[0038] During the falling edge phase, the frequency decreases linearly with time, and the transmitted signal follows Equation 4 during this phase:

[0039] fe(t) = f0 + B - αt;

[0040] The echo signal follows Formula 5:

[0041] fr(t)=f0-f D +B-α(t-τ);

[0042] Beat frequency signals follow Formula Six:

[0043] Δf2=ατ-f D .

[0044] In the above formulas, f e (t) represents the instantaneous frequency of the transmitted signal, which varies with time t; f0 is the starting frequency of the frequency modulation signal (i.e., the frequency at the beginning of the frequency modulation cycle); a is the slope of the frequency modulation, representing the rate at which the frequency increases with time, usually in Hz / s; t is the time variable, representing the moment after the start of the frequency modulation cycle; f r (t) represents the instantaneous frequency of the echo signal, which varies with time t; f D τ is the Doppler frequency shift; B is the time delay; Δf1 is the beat frequency signal at the rising edge; Δf2 is the beat frequency signal at the falling edge.

[0045] FMCW lidar can calculate parameters such as distance and velocity using the above formulas. Specifically, it can be calculated using the following formula. The distance R can be calculated using formula seven:

[0046]

[0047] The velocity v can be calculated using formula eight:

[0048]

[0049] The ranging accuracy δR can be obtained from formula nine:

[0050]

[0051] Where c is the speed of light; T is the frequency modulation period; λ is the wavelength; and v is the radial velocity.

[0052] The above formula describes how FMCW lidar determines the target's distance and velocity by analyzing the beat frequency signals of the rising and falling edges.

[0053] Due to the influence of laser coherence and the coherent detection principle of FMCW, the signal strength detected by radar is directly related to the time difference between the signal light (corresponding to the echo signal mentioned above) and the local oscillator light (corresponding to the transmitted signal mentioned above). From the perspective of FFT (Fast Fourier Transform), the farther the ranging distance, the fewer the effective points of the FFT within one period T. Specifically, the farther the ranging distance, the longer the round-trip time of the signal, and the shorter the effective sampling time of the required frequency components, thus leading to a reduction in the number of effective sampling points. This is manifested as described above. Figure 1The shorter the horizontal line portion of the solid broken line in (b), the greater the pressure on the acquisition system. Furthermore, in principle, as the ranging distance increases, the system's detection frequency will also increase, meaning the aforementioned intermediate frequency will be higher, which will put enormous pressure on the acquisition system.

[0054] To address at least some of the aforementioned problems, embodiments of this application provide a lidar system. For example... Figure 2 As shown, the lidar includes a light source 10, a transmitting module 20, a receiving module 30, a transmission module 40, a detection module 50, and a signal processing module (not shown in the figure).

[0055] The light source 10 is used to provide a laser beam and to separate the laser beam into an oscillator beam and a probe beam.

[0056] The transmitting module 20 is used to receive the detection beam and transmit the detection beam into the detection space.

[0057] The receiving module 30 is used to receive the echo signal; wherein, the echo signal is the beam of light reflected by the object under test after the probe beam passes through the probe space.

[0058] The transmission module 40 includes a first coupler 41 and a plurality of transmission media 42. The local oscillator beam is transmitted through the first coupler 41 to at least one transmission medium 42 for delay processing. The delay amount of the at least one transmission medium 42 is different from the delay amounts of the other transmission media 42.

[0059] The detection module 50 is connected to the transmission module 40 and the receiving module 30, respectively. The detection module 50 is used to receive the echo signal and the delayed local oscillator beam output by the transmission module 40, perform beat frequency processing on the echo signal and the delayed local oscillator beam to obtain the beat frequency signal, and convert the beat frequency signal into a detection electrical signal.

[0060] The signal processing module is electrically connected to the detection module 50. The signal processing module is used to determine the object to be measured based on the detected electrical signal.

[0061] In this embodiment, the light source 10 generally includes a laser 11 and a beam splitter 12, and may also include a collimation module, depending on the application requirements. The beam splitter 12 can be a 1*2 coupler. The transmitting module 20 includes at least a transmitting optical system, which may include lenses, optical fibers, optical chips, etc., depending on the application requirements. The receiving module 30 includes at least a receiving optical system, which may also include lenses, optical fibers, optical chips, etc., depending on the application requirements. It should be noted that the above-mentioned receiving optical system and transmitting optical system can be set separately or integrated into the same optical system, for example, an optical antenna formed on an optical chip, depending on the application requirements.

[0062] The first coupler 41 can be a first beam splitter or a first optical switch, as long as it can transmit the local oscillator beam to at least one transmission medium 42. The transmission medium 42 can be an optical fiber, optical waveguide, etc., and can be selected according to the application requirements. The delay amount of at least one transmission medium 42 is different from the delay amounts of other transmission media 42. This can be achieved by setting delay lines in at least one transmission medium 42, or by making the material of at least one transmission medium 42 different from the material of other transmission media 42. In this embodiment, the delay amount of only one transmission medium 42 can be different from the delay amounts of other transmission media 42, or the delay amounts of multiple transmission media 42 can be different from the delay amounts of other transmission media 42, or the delay amounts of each transmission medium 42 can all be different; the specific settings can be configured according to the application requirements.

[0063] The detection module 50 may include a beater for beat frequency and a photoelectric conversion module for converting the beat frequency signal into a detection electrical signal. The signal processing module may be a central processing unit, a computer, a computer cluster, etc., as long as it can receive the detection electrical signal output by the detection module 50 and calculate the relevant parameters of the object under test based on the detection electrical signal.

[0064] For ease of understanding, we will now take the first coupler 41 as a beam splitter as an example, such as... Figure 2 The working principle of the lidar provided in the embodiments of this application is explained as follows:

[0065] The light source 10 emits a local oscillator beam and a probe beam. The local oscillator beam enters the transmission module 40, is first split into multiple beams by the first coupler 41, and then each beam is transmitted through its respective transmission medium 42. After different delays, it enters the probe module 50.

[0066] During this period, the detection beam is emitted into the detection space via the transmitting module 20. After reaching the object to be measured in the detection space, it is reflected to form an echo signal. The echo signal is received by the receiving module 30 and output to the detection module 50.

[0067] The detection module 50 receives the echo signal and the delayed local oscillator beam output by the transmission module 40. It performs beat frequency processing on the echo signal and the delayed local oscillator beam to obtain a beat frequency signal, which is then converted into a detection electrical signal. The detection electrical signal output by the detection module 50 can be received and processed by the signal processing module. The frequency of the aforementioned beat frequency signal is related to parameters such as the distance and velocity of the object under test. The signal processing module can extract the frequency of the aforementioned beat frequency signal using FFT (Fast Fourier Transform) to calculate parameters such as the distance and velocity of the object under test.

[0068] If the first coupler 41 adopts other structures, such as an optical switch, its principle can be the same as described above. Alternatively, it can guide the local oscillator beam into one or a part of the transmission medium 42 at a certain moment, and guide the local oscillator beam into another or another part of the transmission medium 42 at another moment. The specific method can be determined according to the application requirements.

[0069] In related technologies, at long interference distances, the longer signal propagation time results in fewer effective signal points received within the same sampling time, thus reducing the number of effective points in the Fast Fourier Transform (FFT) and lowering the signal resolution and signal-to-noise ratio. However, the lidar provided in this application embodiment uses multiple transmission media 42 in the transmission module 40, with at least one transmission medium 42 having a different delay than the others. Compared to using only one transmission medium 42 without delay, this allows the local oscillator beam to be split into multiple signals with different delays. Firstly, at long distances, the delay of the local oscillator beam reduces the optical path difference between the echo signal and the local oscillator beam. According to the principle of FMCW lidar, this reduces the frequency of the beat frequency signal, increases the number of effective interference points (i.e., the number of effective FFT points), and thus improves the intensity of the ranging signal at long distances. Secondly, the design of multiple local oscillator beams with different delays in the optical path... The simultaneous operation of the local oscillator circuit allows for signal processing and superposition at the signal end, thereby improving signal strength. Thirdly, the frequency of the beat frequency signal is positively correlated with the ranging distance. At long ranging distances, this increases the bandwidth pressure on the acquisition card and the balanced detector 52. Adding a delay to the local oscillator circuit reduces the frequency of the beat frequency signal, thus reducing the requirements on the acquisition card and the balanced detector 52. Fourthly, adding a delay to the local oscillator circuit can shift the frequency of near-range ranging to a higher frequency. This avoids the negative frequency flipping problem even at high speeds near the near end, thus solving the negative frequency flipping problem caused by high speeds near the near end and ensuring the correctness and stability of the signal.

[0070] The aforementioned laser 11 can be provided by one or more. When multiple lasers 11 are provided, the lidar can provide multiple detection beams, achieving high resolution. The wavelengths of the multiple lasers 11 can be the same or different. When the wavelengths of the multiple lasers 11 are different, the transmitting optical system can be a diffractive emission element, capable of simultaneously emitting multiple detection beams to achieve multi-line scanning, so that different receiving modules 30 can simultaneously receive echo signals of different wavelengths, or receive different echo signals separately.

[0071] In some embodiments, the delay amounts of each transmission medium 42 are different.

[0072] This allows for the acquisition of more signals with varying delays compared to only a portion of the transmission medium 42. This helps improve signal strength and resolution, expands the detectable frequency range, and enhances the overall system performance.

[0073] In some embodiments, the transmission medium 42 has n. n is greater than or equal to n. All n-1 transmission media 42 have delay lines, and when n-1 is greater than or equal to n, the lengths of the delay lines are different.

[0074] The length of the delay line is positively correlated with the delay amount; that is, the longer the delay line, the greater the delay amount.

[0075] In this embodiment, one transmission medium 42 may not have a delay line, and the delay amount of each transmission medium 42 is different. This achieves the advantages of the previous embodiment while reducing the number of delay lines required compared to all transmission media 42 having delay lines, thus lowering the manufacturing cost of the lidar to some extent.

[0076] In some embodiments, the materials of each transmission medium 42 are the same.

[0077] In this way, the delay of each transmission medium 42 can be distinguished by its length, without having to consider other factors, which facilitates the differentiation of the delay of each transmission medium 42 during design and use.

[0078] In some embodiments, the delay line is an optical fiber or an optical waveguide.

[0079] Since there are various types of lidar, the structures and fabrication methods of the components differ depending on the type of lidar. The transmission module 40, in particular, can also be fabricated in multiple ways. For example, when the lidar uses an optical phased array structure, the transmission module 40 can be integrated onto the optical chip; when the lidar uses a non-optical phased array structure, the transmission module can be a separate module. When the transmission module 40 is configured differently, the delay line can be made of different materials and fabricated using different methods.

[0080] Specifically, when the transmission module 40 is located outside the optical chip, or only the delay line is located outside the optical chip, the delay line can be made of optical fiber, which is convenient to source and inexpensive. When the transmission module 40 is located on the optical chip, the delay line can be made of optical waveguide, which facilitates integration and miniaturization of the lidar design.

[0081] like Figure 2 and Figure 3 As shown, in some embodiments, the first coupler 41 is a first beam splitter 411 or a first optical switch 412.

[0082] The first beam splitter 411 is used to split the local oscillator beam into multiple beams. For example... Figure 2As shown, when the first coupler 41 uses the first beam splitter 411, the local oscillator beam is split into multiple beams by the first beam splitter 411. Each beam is then subjected to beat frequency after passing through a different delay path (i.e., transmission medium 42). This method can simultaneously acquire multiple signals, and by accumulating the distance signals corresponding to different local oscillator paths, the signal strength can be further improved.

[0083] like Figure 3 As shown, an optical switch is a device capable of switching between different optical paths, used to control the on / off state of different optical paths. Depending on the specific material of the transmission medium 42, the first optical switch 412 can be selected to be compatible with the transmission medium 42. For example, if the transmission medium 42 is an optical fiber, the first optical switch 412 can be a fiber optic switch; if the transmission medium 42 is a waveguide, the first optical switch 412 can be a waveguide switch. When the first coupler 41 uses the first optical switch 412, the on / off state of different transmission media 42 can be controlled by the first optical switch 412, allowing selective switching of different transmission media 42 according to usage needs. This makes it suitable for various operating environments and has a wide range of applications.

[0084] like Figure 3 As shown, in some embodiments, the transmission module 40 further includes a second coupler 43. The second coupler 43 has multiple receiving ends and one output end. The receiving ends are connected one-to-one with the transmission medium 42. The second coupler 43 is used to receive the delayed local oscillator beam and provide it to the detection module 50.

[0085] The lidar corresponding to this embodiment is a single-transmitter, single-receiver radar. The structures of the first coupler 41 and the second coupler 43 in this embodiment can be the same or different. For example, one of the couplers 41 and 43 can be an optical switch, and the other can be a beam splitter or a beam combiner. Alternatively, both couplers can be optical switches, or one coupler can be a beam splitter and the other coupler can be a beam combiner.

[0086] In this embodiment, the number of receiving modules 30 and detection modules 50 is small, which reduces the number of components required for the lidar, making the structure simple and easy to assemble.

[0087] In some embodiments, the second coupler 43 is a first beam combiner or a second optical switch.

[0088] When the second coupler 43 is the first beam combiner (not shown in the figure) and the first coupler 41 is the beam splitter, the lidar can simultaneously adapt to ranging environments with different distances.

[0089] like Figure 3As shown, when the first coupler 41 adopts the first optical switch 412 and the second coupler 43 adopts the second optical switch, compared with the scheme of using a beam splitter to split the local oscillator light and using a first beam combiner to combine the multiple local oscillator lights after delay processing, firstly, using two optical switches can reduce optical loss; secondly, since both couplers are optical switches, different delay paths can be selectively switched according to the needs of use, thereby making the frequency component in the beat frequency signal singular and simplifying the frequency calculation algorithm.

[0090] like Figure 4 As shown, in some embodiments, the receiving module 30 includes multiple receiving units 31. The detection module 50 includes multiple detection units. The transmission medium 42, the receiving unit 31, and the detection unit correspond one-to-one.

[0091] The detection unit receives the delayed local oscillator beam provided by the transmission medium 42 and the echo signal provided by the receiving unit 31, performs frequency beating, obtains the frequency beating signal, and converts the frequency beating signal into a detection electrical signal.

[0092] In this embodiment, the receiving unit 31 can be two, three, or more, depending on the application requirements. The lidar corresponding to this embodiment can be a one-transmitter-two-receiver radar or a one-transmitter-multiple-receiver radar.

[0093] Using the solution provided in this embodiment, the number of receiving units 31 in the receiving module 30 is relatively large, which can receive more echo signals and help improve the detection accuracy of the lidar.

[0094] In some embodiments, the detection unit includes a second beam combiner 51 and a balanced detector 52. The second beam combiner 51 is used to receive the echo signal and the delayed local oscillator beam output by the transmission module 40, and to perform beat frequency processing on the echo signal and the delayed local oscillator beam to obtain a beat frequency signal. The balanced detector 52 is used to convert the beat frequency signal into a detection electrical signal.

[0095] The second combiner 51 is selected according to the material of the transmission medium 42. Specifically, when the transmission medium 42 is optical fiber, the second combiner 51 can be an optical fiber coupler; when the transmission medium 42 is optical waveguide, the second combiner 51 can be a waveguide coupler.

[0096] A balanced detector 52 is a device used to detect optical signals. It typically consists of two matched photodetectors, whose output signals are processed by a differential amplifier. The main purpose of the balanced detector 52 is to eliminate common-mode noise and improve the signal-to-noise ratio.

[0097] The solution provided in this embodiment can eliminate environmental noise and fluctuations in the laser 11 to a certain extent, thereby improving the measurement accuracy of the lidar.

[0098] The above description is merely a preferred embodiment of the present invention and only specifically describes the technical principles of the present invention. These descriptions are only for explaining the principles of the present invention and should not be construed as limiting the scope of protection of the present invention in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention, as well as other specific embodiments of the present invention that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of the present invention.

Claims

1. A lidar, characterized in that, include: A light source is used to provide a laser beam and to split the laser beam into an oscillating beam and a probe beam; A transmitting module is used to receive the detection beam and transmit the detection beam into the detection space; A receiving module is used to receive echo signals, wherein the echo signals are the beams of light reflected by the probe beam after passing through the object under test in the probe space; A transmission module includes a first coupler and a plurality of transmission media, wherein the local oscillator beam is transmitted to at least one of the transmission media for delay processing via the first coupler, wherein the delay amount of the at least one transmission medium is different from the delay amount of the other transmission media; The detection module is connected to the transmission module and the receiving module respectively, and is used to receive the echo signal and the delayed local oscillator beam output by the transmission module, perform beat frequency processing on the echo signal and the delayed local oscillator beam to obtain a beat frequency signal, and convert the beat frequency signal into a detection electrical signal; A signal processing module, electrically connected to the detection module, is used to determine the object to be tested based on the detection electrical signal.

2. The lidar as described in claim 1, characterized in that, The delay amounts of each of the aforementioned transmission media are different.

3. The lidar as described in claim 1, characterized in that, The transmission medium is provided with n, where n is greater than or equal to 2. Each of the n-1 transmission media is provided with a delay line, and when n-1 is greater than or equal to 2, the length of each delay line is different.

4. The lidar as described in claim 3, characterized in that, The materials of all the transmission media are the same.

5. The lidar as described in claim 3, characterized in that, The delay line is an optical fiber or an optical waveguide.

6. The lidar as described in claim 1, characterized in that, The first coupler is a first beam splitter or a first optical switch.

7. The lidar as described in any one of claims 1-6, characterized in that, The transmission module further includes a second coupler, which has multiple receiving ends and one output end, and the receiving ends are connected to the transmission medium in a one-to-one correspondence. The second coupler is used to receive the delayed local oscillator beam and provide it to the detection module.

8. The lidar as described in claim 7, characterized in that, The second coupler is either a first beam combiner or a second optical switch.

9. The lidar as described in any one of claims 1-6, characterized in that, The receiving module includes multiple receiving units, the detection module includes multiple detection units, and the transmission medium, the receiving unit, and the detection unit correspond one-to-one; The detection unit receives the delayed local oscillator beam provided by the transmission medium and the echo signal provided by the receiving unit, performs beat frequency analysis to obtain the beat frequency signal, and converts the beat frequency signal into the detection electrical signal.

10. The lidar as described in any one of claims 1-6, characterized in that, The detection unit includes a second beam combiner and a balanced detector. The second beam combiner is used to receive the echo signal and the delayed local oscillator beam output by the transmission module, and to perform beat frequency processing on the echo signal and the delayed local oscillator beam to obtain the beat frequency signal. The balanced detector is used to convert the beat frequency signal into the detection electrical signal.

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