CN117949924A - Pulse laser radar and detection method - Google Patents

Abstract

The application relates to a pulse laser radar and a detection method. The pulse laser radar includes: the device comprises a laser module, a first coupler, a modulator, a first beam splitter, a circulation module, a processing module and a detection module. The method comprises the steps that first continuous laser and circulating light are coupled into first coupled light and then output to a modulator, the modulator carries out frequency modulation and pulse modulation on the first coupled light to obtain first modulated light, and the first modulated light is split by a first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; therefore, the more the number of modulations, the greater the frequency shift and extinction ratio. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators.

Description

Pulse laser radar and detection method

Technical Field

The invention relates to the technical field of laser radars, in particular to a pulse laser radar and a detection method.

Background

With the development of lidar technology, pulsed lidar technology has emerged. In pulsed lidar, extinction ratio is a very important parameter. Especially for coherent system radar, the insufficient extinction ratio of the system can seriously influence the detection result of the radar on weak signals.

At present, means such as an acousto-optic modulator, an electro-optic modulator, a semiconductor optical amplifier and the like are commonly used for carrying out pulse modulation on light beams. However, for coherent radar with weak signal detection, it is difficult for a single device to achieve the extinction ratio required by the system. Often, a plurality of modulators are cascaded to achieve ultra-high extinction ratios.

When the laser radar detects signals, certain errors are unavoidable. At present, abnormal data are usually identified and removed through an algorithm, or removed data are complemented by adopting an interpolation method, so that the influence of the abnormal data can be greatly reduced, but the real situation cannot be reflected.

Disclosure of Invention

In view of the foregoing, it is necessary to provide a pulsed laser radar and a detection method capable of reducing a detection error of the laser radar and improving a extinction ratio of the system.

In a first aspect, the present application provides a pulsed lidar comprising:

the laser module is used for outputting first continuous laser and second continuous laser;

the first coupler is used for receiving the first continuous laser and the circulating light, coupling the first continuous laser and the circulating light into first coupled light and outputting the first coupled light;

The modulator is used for receiving the first coupling light output by the first coupler, and carrying out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light;

The first beam splitter is used for receiving the first modulated light and splitting the first modulated light to obtain light to be recycled and second modulated light;

The circulating module is used for receiving light to be circulated, converting the light to be circulated into circulating light and transmitting the circulating light to the first coupler;

The processing module is used for receiving the second modulated light, transmitting the second modulated light to the target to be detected and receiving echo signals reflected back by the target to be detected;

And the detection module is used for converting the echo signal and the second continuous laser into an electric signal after coupling.

In one embodiment, the circulation module includes: and the optical amplifier is used for receiving the light to be circulated to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

In one embodiment, the recycled light includes at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one modulated optical signal at least one time the modulation frequency shift.

In one embodiment, the splitting ratio of the first beam splitter is between 1:1 and 9:1.

In one embodiment, the detection module comprises: the second coupler is used for coupling the echo signal and the second continuous laser to obtain a coupled optical signal;

and the detector receives the coupling optical signals, beats the coupling optical signals, and converts the beaten coupling optical signals into electric signals.

In a second aspect, the present application also provides a pulse lidar detection method, the method comprising:

controlling the laser module to output first continuous laser and second continuous laser;

Receiving the first continuous laser and the circulating light through a first coupler, coupling the first continuous laser and the circulating light into first coupled light, and outputting the first coupled light;

Receiving the first coupling light output by the first coupler through a modulator, and performing frequency modulation and pulse modulation on the first coupling light to obtain first modulated light;

receiving the first modulated light by adopting a first beam splitter, and splitting the first modulated light to obtain light to be recycled and second modulated light;

Receiving light to be circulated through a circulation module, converting the light to be circulated into circulating light and transmitting the circulating light to a first coupler;

Receiving the second modulated light through the processing module, transmitting the second modulated light to the target to be detected, and receiving an echo signal reflected back by the target to be detected;

the echo signal and the second continuous laser are coupled through the detection module and then converted into an electric signal.

In one embodiment, receiving the light to be recycled by the recycling module, converting the light to be recycled into recycled light for transmission to the first coupler includes:

And receiving the light to be circulated through the optical amplifier to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

In one embodiment, the recycled light includes at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one modulated optical signal at least one time the modulation frequency shift.

In one embodiment, receiving the first modulated light with a first beam splitter, and splitting the first modulated light to obtain the light to be recycled and the second modulated light includes:

and receiving the first modulated light by using a first beam splitter with the light splitting ratio of 1:1 to 9:1, and splitting the first modulated light to obtain light to be recycled and second modulated light, wherein the ratio of the light to be recycled to the second modulated light corresponds to the light splitting ratio of the first beam splitter.

In one embodiment, coupling the echo signal and the second continuous laser light through a detection module and converting the echo signal and the second continuous laser light into electrical signals includes:

coupling the echo signal and the second continuous laser through a second coupler to obtain a coupled optical signal;

And receiving the coupled optical signal through the detector, beating the coupled optical signal, and converting the beaten coupled optical signal into an electric signal.

According to the pulse laser radar and the detection method, the first continuous laser and the circulating light are coupled into the first coupling light and then output to the modulator, the modulator carries out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light, and the first modulated light is split by the first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; therefore, the more the modulation times, the larger the frequency shift and extinction ratio, and the larger the frequency shift and the higher the extinction ratio in the frequency domain, the frequency can be selected according to the extinction ratio required by the system. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators. Furthermore, the pulse laser radar provided by the application has less error sources and reduced adjustment complexity because of less adjustment parameters; and the pulse laser radar provided by the application also reduces the uncertainty of the test result due to the adoption of the same modulator for cyclic modulation.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a pulsed lidar in one embodiment;

FIG. 2 is a schematic diagram of a pulsed lidar in another embodiment;

FIG. 3 is a flow chart of a method of pulsed lidar detection in one embodiment;

fig. 4 is a flow chart of a pulse lidar detection method according to another embodiment.

Detailed Description

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

In one exemplary embodiment, as shown in fig. 1, a pulsed lidar is provided, the lidar comprising: a laser module 102 for outputting a first continuous laser and a second continuous laser; a first coupler 104 for receiving the first continuous laser light and the circulating light, coupling the first continuous laser light and the circulating light into first coupled light, and outputting the first coupled light; a modulator 106, configured to receive the first coupled light output by the first coupler 104, and perform frequency modulation and pulse modulation on the first coupled light to obtain first modulated light; a first beam splitter 108, configured to receive the first modulated light, and split the first modulated light to obtain light to be recycled and second modulated light; the recycling module 110 is configured to receive light to be recycled, convert the light to be recycled into recycled light, and transmit the recycled light to the first coupler 104; the processing module 112 is configured to receive the second modulated light, transmit the second modulated light onto the target to be measured, and receive an echo signal reflected back by the target to be measured; the detection module 114 is configured to couple and convert the echo signal and the second continuous laser to an electrical signal.

The extinction ratio is defined as the ratio of the optical power P1 when operating at a high level to the optical power P0 when operating at a low level after the laser light of the laser is input to the modulator. For coherent system radar, insufficient extinction ratio of the system can seriously influence the detection result of the laser radar on weak signals. At present, an acousto-optic modulator, an electro-optic modulator, a semiconductor optical amplifier and other means are commonly used for pulse modulation, and for coherent radar for weak signal detection, the extinction ratio required by a system is difficult to achieve by a single device. Often, multiple modulators are cascaded to achieve ultra-high extinction ratios, making the system complex and error-rich.

To solve the above problem, one embodiment of the present application provides a pulse laser radar including a laser module 102, a first coupler 104, a modulator 106, a first beam splitter 108, a circulation module 110, a processing module 112, and a detection module 114.

The laser module 102 is configured to output continuous laser, one of which is a first continuous laser transmitted to the first coupler 104 as signal light, and one of which is a second continuous laser transmitted to the detector module as local oscillation light; the first coupler 104 is configured to couple the first continuous laser light emitted by the laser module 102 as the signal light and the circulating light of the circulating module 110 and transmit the coupled first continuous laser light and circulating light to the modulator 106; the modulator 106 performs frequency modulation and pulse modulation on the light coupled by the first coupler 104, and generates a pulse light signal, i.e. the first modulated light. The frequency of the pulse optical signal relative to the frequency of the input continuous light is shifted, the frequency shift is determined by the characteristics of the modulator 106, the insertion loss of the modulator 106 determines the peak power of the pulse, the turn-off performance of the modulator 106 determines the pulse leakage power when the light is turned off, and the ratio of the peak power to the pulse leakage power is the extinction ratio of the modulator, namely the modulator 106 can provide the pulse light with a certain extinction ratio; the first beam splitter 108 splits the light modulated by the modulator 106 into two parts, one part being transmitted to the recycling module 110 and the other part being transmitted to the processing module 112; the recycling module 110 receives a portion of the light split by the first beam splitter, which is transmitted to the first coupler 104; the processing module is configured to further amplify, transmit, receive and send the second modulated light transmitted from the first beam splitter 108, and according to the characteristics of the target to be detected, the processing module 112 needs to amplify the modulated pulse signal to a specific power, then transmit the modulated pulse signal to the target to be detected, and transmit an echo signal reflected by the target to be detected to the detection module 114; the detection module 114 is configured to optically couple the echo signal and a second continuous laser, i.e., a local oscillator, and convert the echo signal and the second continuous laser into an electrical signal.

According to the pulse laser radar, the first continuous laser and the circulating light are coupled into the first coupling light and then output to the modulator, the modulator carries out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light, and the first modulated light is split by the first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; therefore, the more the modulation times, the larger the frequency shift and extinction ratio, and the larger the frequency shift and the higher the extinction ratio in the frequency domain, the frequency can be selected according to the extinction ratio required by the system. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators. Furthermore, the pulse laser radar provided by the application has less error sources and reduced adjustment complexity because of less adjustment parameters; and the pulse laser radar provided by the application also reduces the uncertainty of the test result due to the adoption of the same modulator for cyclic modulation.

In one exemplary embodiment, the laser module 102 includes: a laser for outputting continuous laser light; and a second beam splitter for receiving the continuous laser light and dividing the continuous laser light into a first continuous laser light and a second continuous laser light.

In one exemplary embodiment, the circulation module includes: and the optical amplifier is used for receiving the light to be circulated to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

Specifically, the circulating light is amplified by the optical amplifier, and the circulating light transmitted to the first coupler is delayed to the next pulse period or the subsequent pulse period by the delay optical fiber, so as to ensure that the pulse light beams coincide.

In this embodiment, by amplifying and delaying the circulating light, it can be ensured that the pulse light beams incident to the modulator overlap, so as to obtain a better modulation waveform, facilitate subsequent processing of the echo signal, and avoid the problem that the echo signal cannot be resolved or is not easy to resolve.

In one embodiment, the recycled light includes at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one modulated optical signal at least one times the modulation frequency shift.

It will be appreciated that circulating light is a beam of light that is frequency modulated and pulsed via a modulator. Specifically, the modulator modulates the frequency of the light beam incident therein to shift the frequency of the light beam, so that the direction of Doppler shift of the target to be detected can be obtained when heterodyne detection is performed on the light beam.

The heterodyne detection is to mix the laser generated by a beam of local oscillation with the input signal light in an optical mixer to obtain a signal with the frequency, phase and amplitude of the signal light changing according to the same rule. In coherent system radar, heterodyne detection technology is often adopted, and the speed of a target object is calculated through the frequency difference between a local oscillation signal and an echo signal, and the relation is as follows: doppler shift = speed of target object/laser wavelength. Because heterodyne detection cannot detect the direction of doppler shift, signal light is often subjected to frequency modulation before being transmitted, so that the transmitted laser and local oscillation light generate intermediate frequency, and the doppler shift=the frequency difference-intermediate frequency between the local oscillation signal and the echo signal.

Illustratively, the signal light and the local oscillation light interfere with each other on the surface of the detector, and a difference frequency signal of the signal light and the local oscillation light is output through the photoelectric detector. In addition, the signal optical electric field on the detector plane is u _sd, and the local oscillation optical electric field is u _od, so that the electric field distribution u _d on the detector plane can be represented as the sum of u _sd and u _od. The field strength distribution in the detector plane at a certain moment can thus be shown in formula (1):

I_d(x,y,t)＝|u_d(x,y,t)|²＝|u_od(x,y,t)|²+|u_sd(x,y,t)|²

+2Re[u_od(x,y,t)^*u_sd(x,y,t)]

＝I_sd(x,y,t)+I_od(x,y,t)+I_h(x,y,t) (1)

In the formula (1), I _sd (x, y, t) is the field intensity of the signal light, I _od (x, y, t) is the field intensity of the local oscillation light, and I _h (x, y, t) is the coherence term between the local oscillation light and the signal light. In the coherent detection process, in order to obtain positive and negative information of doppler shift, an inherent difference frequency, called intermediate frequency Δv _IF, exists between the signal light and the local station light. In the application, the first coupling light incident to the modulator is shifted by the modulator to obtain the first modulated light, so that the frequency difference between the light beam of the first modulated light and the light beam of the second continuous laser, which is local oscillation light, is the intermediate frequency. Thus, the field strength of the heterodyne signal can be expressed by equation (2):

In the formula (2), delta phi (x, y, t) is the phase difference between the signal light emitted by the pulse laser radar and the local oscillation light. Since the detector detects a time average value of the optical signal over a period of time, I _sd(x,y,t),I_od (x, y, t) is a direct current component, which can be directly filtered by a filter. The frequency of I _h (x, y, z, t) is the frequency difference Deltav _IF +Deltav between the local oscillation light and the signal light, and the coherent signal frequency is extracted through signal processing, so that the Doppler frequency shift of the target to be detected is obtained, and the direction of the Doppler frequency shift can be further obtained.

For example, please refer again to fig. 1. As shown in fig. 1, when the first continuous laser light output by the laser module 102 is sent to the modulator 106 after passing through the first coupler 104, a first pulse signal is generated, the extinction ratio of which is denoted as modulation extinction ratio EX, and the frequency shift of which is denoted as modulation shift frequency Δf; a part of the modulated pulse signal is transmitted to the circulation module 110 through the first beam splitter 108, and is mixed with the first continuous laser light through the first coupler 104 and then modulated by the modulator 106 to generate a second pulse signal, wherein the pulse comprises two signals of which the extinction ratio is a modulation extinction ratio EX, the frequency shift is a modulation shift frequency delta f, the extinction ratio is twice the modulation extinction ratio 2EX, and the frequency shift is twice the modulation shift frequency 2 delta f; similarly, the third pulse signal includes three signals of a extinction ratio of modulation extinction ratio EX, a frequency shift of modulation shift Δf, a extinction ratio of twice modulation extinction ratio 2EX, a frequency shift of twice modulation shift 2Δf, a extinction ratio of triple modulation extinction ratio 3EX, and a frequency shift of triple modulation shift 3Δf after the third pulse modulation; after which each modulation is increased by one extinction and one shift.

That is, the pulse lidar in this embodiment can obtain a plurality of light beams with different intermediate frequencies at the same time, and these light beams with different intermediate frequencies also have a plurality of different extinction ratios, and illustratively, the present application can obtain the following light beams at the same time:

(1) Extinction ratio EX, light with frequency shift delta f;

(2) Light with extinction ratio of 2EX and frequency shift of 2 delta f;

(3) Light with extinction ratio of 3EX and frequency shift of 3 Deltaf;

...

Therefore, the more the modulation times, the larger the frequency shift and extinction ratio, and the larger the frequency shift and the higher the extinction ratio in the frequency domain, the frequency can be selected according to the extinction ratio required by the system.

Thus, there are a plurality of frequencies which meet the extinction ratio, and all the frequencies can be used as detection intermediate frequency; multimodal probing can be achieved by selecting multiple frequencies. By way of example, two frequencies with shift frequencies of 2Δf and 3Δf are selected as intermediate frequencies, two Doppler frequency shifts can be obtained according to the two intermediate frequencies during signal processing, and an average value of the two Doppler frequency shifts is taken as a final Doppler frequency shift, so that errors of single-peak detection can be reduced; that is, multimodal probing can improve measurement accuracy.

In this embodiment, since the circulating light includes at least one beam of modulated optical signals, where the extinction ratio of the at least one beam of modulated optical signals is at least one time of the modulation extinction ratio, the frequency shift of the at least one beam of modulated optical signals is at least one time of the modulation frequency shift, so that the pulse laser radar has pulse signals with various frequencies and extinction ratios, and thus the frequency can be selected according to the extinction ratio required by the pulse laser radar, and accurate detection of the echo signal can be achieved.

In one exemplary embodiment, the first beam splitter has a split ratio of between 1:1 and 1:9.

Specifically, the power duty cycle of different frequencies can be changed by changing the split ratio of the first beam splitter 108. In one exemplary embodiment, the first beam splitter 108 has a split ratio of 1:1, the amplification factor of the optical amplifier is 10 times, the power of the first pulse signal generated by the modulator 106 is P0, and all devices have no insertion loss; after passing through the first beam splitter 108, the optical power of the circulating light sent to the optical amplifier is 0.5P0, and the optical power sent to the processing module 112 is 0.5P0; after passing through the optical amplifier, the optical power of the circulating light is 5P0; after the second modulation, the modulator 106 generates a second pulse signal, where the extinction ratio is a modulation extinction ratio EX, the pulse signal optical power shifted by a modulation shift Δf is P0, and the pulse signal optical power shifted by a modulation shift 2Δf is 5P 0. After the second pulse signal passes through the first beam splitter 108, the pulse signal light sent to the processing module 112 is a pulse signal with a extinction ratio of modulation extinction ratio EX, a frequency shift of modulation shift Δf, optical power of 0.5P0, and a pulse signal with a extinction ratio of twice modulation extinction ratio 2EX, a frequency shift of twice modulation shift 2Δf, and optical power of 2.5P0; since the extinction ratio is the modulation extinction ratio EX, the pulse signal light shifted by the modulation shift frequency Δf, and the extinction ratio is the double modulation extinction ratio 2EX, the pulse signal light power ratio shifted by the double modulation shift frequency 2Δf is 0.5:2.5, i.e. 1:5. the optical power ratio of the pulse signal light with different extinction ratios and frequency shifts after the Nth frequency shift is similar. It will be appreciated that when the optical amplifier has a magnification of 1, it can be considered that there is no optical amplifier device in the recycling module.

In one exemplary embodiment, the first beam splitter 108 has a split ratio of 9:1, the amplification factor of the optical amplifier is 10 times, the power of the first pulse signal generated by the modulator 108 is P0, and all devices have no insertion loss; after passing through the first beam splitter 108, the optical power of the circulating light sent to the optical amplifier is 0.9P0, and the optical power sent to the processing module 112 is 0.1P0; after passing through the optical amplifier, the optical power of the circulating light is 9P0; after the second modulation, the modulator 106 generates a second pulse signal, where the extinction ratio is a modulation extinction ratio EX, the pulse signal optical power shifted by a modulation shift Δf is P0, and the pulse signal optical power shifted by a modulation shift 2Δf is 9P0; after the second pulse signal passes through the first beam splitter 108, the pulse signal light sent to the processing module 112 is a pulse signal with a extinction ratio of modulation extinction ratio EX, a frequency shift of modulation shift Δf, optical power of 0.1P0, and a pulse signal with a extinction ratio of twice modulation extinction ratio 2EX, a frequency shift of twice modulation shift 2Δf, and optical power of 0.9P0; since the extinction ratio is the modulation extinction ratio EX, the pulse signal light shifted by the modulation shift frequency Δf, and the extinction ratio is the double modulation extinction ratio 2EX, the pulse signal light power ratio shifted by the double modulation shift frequency 2Δf is 0.1:0.9, i.e. 1:9. the optical power ratio of the pulse signal light with different extinction ratios and frequency shifts after the Nth frequency shift is similar.

Further, the ratio of the optical power of the pulse signal may take into account the loss of the device and the amplifying capability of the amplifier.

In this embodiment, the split ratio of the first beam splitter is between 1:1 and 1:9, and the power ratio of the pulse signals with different frequencies can be changed by changing the split ratio of the first beam splitter, so as to obtain pulse signals with multiple frequencies, and realize multimodal detection, thereby improving measurement accuracy.

In one exemplary embodiment, a detection module of a pulsed lidar includes: the second coupler is used for coupling the echo signal and the second continuous laser to obtain a coupled optical signal; and the detector receives the coupling optical signals, beats the coupling optical signals, and converts the beaten coupling optical signals into electric signals.

Further, the detector is a balanced detector.

For example, when coherent detection can be performed, the coherent laser signal and the local oscillation signal are incident on the photosensitive surface of the detector together under the condition of meeting wavefront matching, so that beat frequency or coherent superposition is generated, and the magnitude of the output electric signal of the detector is in direct proportion to the square of the sum of the laser signal (echo signal) to be detected and the local oscillation signal. When the second continuous laser, namely the local oscillation light and the echo signal are received by the balance detector at the same time, the balance detector is in a coherent detection state, and the signal section is processed by the balance detector, so that the output electric signal of the balance detector is in direct proportion to the square of the sum of the echo signal and the local oscillation signal.

In the embodiment, a method of coherent detection is adopted for the target to be detected, and the coupled optical signals are subjected to beat frequency and then converted into the electric signals, so that a high-precision detection result of the target to be detected can be obtained; furthermore, by adopting the balance detector for detection, noise and interference signals can be counteracted, and only required signal components are reserved, so that the quality of signals is improved, and the signal-to-noise ratio of the signals is effectively improved.

In one embodiment, please refer to fig. 2, which is a schematic diagram of a pulse laser radar according to another embodiment. As shown in fig. 2, the pulse lidar includes: a laser for outputting continuous laser light; a second beam splitter for receiving the continuous laser light and dividing the continuous laser light into a first continuous laser light and a second continuous laser light; a first coupler 104 for receiving the first continuous laser light and the circulating light, coupling the first continuous laser light and the circulating light into first coupled light, and outputting the first coupled light; a modulator 106, configured to receive the first coupled light output by the first coupler 104, and perform frequency modulation and pulse modulation on the first coupled light to obtain first modulated light; the first beam splitter 108 is configured to receive the first modulated light, and split the first modulated light to obtain light to be recycled and second modulated light, where optionally, the splitting ratio of the first beam splitter is between 1:1 and 9:1; an optical amplifier 1102 for receiving the light to be recycled to obtain recycled light, amplifying and delaying the recycled light, and transmitting the recycled light to the first coupler 104, wherein the recycled light comprises at least one beam of modulated optical signals, the extinction ratio of the at least one beam of modulated optical signals is at least one time of the modulation extinction ratio, and the frequency shift of the at least one beam of modulated optical signals is at least one time of the modulation frequency shift; the processing module 112 is configured to receive the second modulated light, transmit the second modulated light onto the target to be measured, and receive an echo signal reflected back by the target to be measured; a second coupler 1142, where the second coupler 1142 is configured to couple the echo signal and the second continuous laser to obtain a coupled optical signal; the detector 1144, the detector 1144 receives the coupled light signal, beats the coupled light signal, and converts the beaten coupled light signal into an electrical signal, and the detector 1144 is an optional balanced detector.

Illustratively, the pulsed lidar includes a laser, a second beam splitter, a first coupler 104, a modulator 106, a first beam splitter 108, an optical amplifier 1102, a processing module 112, a second coupler 1142, and a balanced detector.

The laser is used for outputting continuous laser, the continuous laser is divided into two paths through the second beam splitter, one path is first continuous laser which is transmitted to the first coupler 104 as signal light, and the other path is second continuous laser which is transmitted to the second coupler 1142 as local oscillation light; the first coupler 104 is configured to couple the first continuous laser light and the circulating light output by the optical amplifier to obtain first coupled light and transmit the first coupled light to the modulator 106; the modulator 106 performs frequency modulation and pulse modulation on the incident first coupled light to generate a pulse light signal, namely first modulated light, the first modulated light generates a frequency shift relative to the frequency of the continuous laser output by the laser, the frequency shift is determined by the characteristics of the modulator, the insertion loss of the modulator determines the magnitude of pulse peak power, the turn-off performance of the modulator determines the magnitude of pulse leakage power when the light is turned off, and the ratio of the peak power to the pulse leakage power is the extinction ratio of the modulator, namely the modulator 106 can provide pulse light with a certain extinction ratio, namely the first modulated light; the first beam splitter 108 splits the light emitted by the modulator into two parts, one part being the light to be fed back to the optical amplifier and the other part being the second modulated light to the processing module 112; the optical amplifier 110 receives the light to be fed back separated by the first beam splitter 108, converts the light to be fed back into feedback light, amplifies the feedback light, and delays the amplified light and transmits the delayed light to the first coupler 104; the processing module 112 is configured to further amplify, transmit, receive, and send the second modulated light, and according to the characteristics of the target to be tested, the processing module 112 needs to amplify the modulated second modulated light to a specific power, then transmit the second modulated light to the target to be tested, and transmit an echo signal reflected by the target to be tested to the second coupler 1142. The second coupler 1142 mixes the echo signal with the second continuous laser beam as the local oscillation light and transmits the mixed laser beam to the balance detector. The balance detector receives the two coupled signals, and performs beat frequency conversion to an electric signal.

According to the pulse laser radar, the first continuous laser and the circulating light are coupled into the first coupling light and then output to the modulator, the modulator carries out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light, and the first modulated light is split by the first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; thus, the more the number of modulations, the greater the frequency shift and extinction ratio, and in the frequency domain the greater the frequency shift and the higher the extinction ratio, the frequency can be selected according to the extinction ratio desired by the system, wherein the recycled light comprises at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and at least one times the frequency shift of the modulation. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators; the pulse laser radar provided by the application has less error sources and reduced adjustment complexity because of less adjustment parameters; the pulse laser radar provided by the application adopts the same modulator to circularly modulate, so that the uncertainty of a test result is reduced; furthermore, multimodal detection can be realized by selecting a plurality of frequencies, so that the error of unimodal detection can be reduced; that is, multimodal probing can improve measurement accuracy.

Based on the same inventive concept, the embodiment of the present application further provides a pulse laser radar detection method, referring to fig. 3, fig. 3 is a schematic flow chart of the pulse laser radar detection method in one embodiment, where the pulse laser radar detection method in any one of the foregoing embodiments is used, and the pulse laser radar detection method includes:

In step 302, the laser module is controlled to output a first continuous laser and a second continuous laser.

Step 304, receiving the first continuous laser and the circulating light through the first coupler, and coupling the first continuous laser and the circulating light into first coupled light and outputting the first coupled light.

Step 306, receiving the first coupled light output by the first coupler through the modulator, and performing frequency modulation and pulse modulation on the first coupled light to obtain first modulated light.

In step 308, the first beam splitter is used to receive the first modulated light, and the first modulated light is split to obtain the light to be recycled and the second modulated light.

In step 310, the light to be recycled is received by the recycling module, and is converted into recycled light and transmitted to the first coupler.

In step 312, the processing module receives the second modulated light, emits the second modulated light onto the target to be measured, and receives the echo signal reflected back by the target to be measured.

In step 314, the echo signal and the second continuous laser are coupled by the detection module and then converted into an electrical signal.

According to the pulse laser radar detection method, the first continuous laser and the circulating light are coupled into the first coupling light and then output to the modulator, the modulator is used for carrying out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light, and the first modulated light is split by the first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; therefore, the more the modulation times, the larger the frequency shift and extinction ratio, and the larger the frequency shift and the higher the extinction ratio in the frequency domain, the frequency can be selected according to the extinction ratio required by the system. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators. Furthermore, the pulse laser radar provided by the application has less error sources and reduced adjustment complexity because of less adjustment parameters; and the pulse laser radar provided by the application also reduces the uncertainty of the test result due to the adoption of the same modulator for cyclic modulation.

In one embodiment, controlling the laser module to output the first continuous laser light and the second continuous laser light includes:

Controlling the laser to output continuous laser; the continuous laser light is received by the second beam splitter and split into a first continuous laser light and a second continuous laser light.

In one embodiment, receiving the light to be recycled by the recycling module, converting the light to be recycled into recycled light for transmission to the first coupler comprises:

And receiving the light to be circulated through the optical amplifier to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

In this embodiment, by amplifying and delaying the circulating light, it can be ensured that the pulse light beams incident to the modulator overlap, so as to obtain a better modulation waveform, facilitate subsequent processing of the echo signal, and avoid the problem that the echo signal cannot be resolved or is not easy to resolve.

In one embodiment, the recycled light includes at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one modulated optical signal at least one times the modulation frequency shift.

In this embodiment, since the circulating light includes at least one beam of modulated optical signals, where the extinction ratio of the at least one beam of modulated optical signals is at least one time of the modulation extinction ratio, the frequency shift of the at least one beam of modulated optical signals is at least one time of the modulation frequency shift, so that the pulse laser radar has pulse signals with various frequencies and extinction ratios, and thus the frequency can be selected according to the extinction ratio required by the pulse laser radar, and accurate detection of the echo signal can be achieved.

In one embodiment, receiving the first modulated light with a first beam splitter and splitting the first modulated light to obtain the light to be recycled and the second modulated light includes:

And receiving the first modulated light by using a first beam splitter with the light splitting ratio of 1:1 to 9:1, and splitting the first modulated light to obtain light to be recycled and second modulated light, wherein the ratio of the light to be recycled to the second modulated light corresponds to the light splitting ratio of the first beam splitter.

In this embodiment, the first beam splitter with a beam splitting ratio between 1:1 and 1:9 is used to receive the first modulated light, and the power ratio of the pulse signals with different frequencies can be changed by changing the beam splitting ratio of the first beam splitter, so as to obtain the pulse signals with multiple frequencies, and realize multimodal detection, thereby improving measurement accuracy.

In one embodiment, coupling the echo signal and the second continuous laser light through the detection module and converting the echo signal and the second continuous laser light into electrical signals includes:

coupling the echo signal and the second continuous laser through a second coupler to obtain a coupled optical signal;

And receiving the coupled optical signal through the detector, beating the coupled optical signal, and converting the beaten coupled optical signal into an electric signal.

Further, the coupled optical signal is received by the balance detector, beat frequency is carried out on the coupled optical signal, and the beat frequency coupled optical signal is converted into an electric signal.

In the embodiment, a method of coherent detection is adopted for the target to be detected, and the coupled optical signals are subjected to beat frequency and then converted into the electric signals, so that a high-precision detection result of the target to be detected can be obtained; furthermore, by adopting the balance detector for detection, noise and interference signals can be counteracted, and only required signal components are reserved, so that the quality of signals is improved, and the signal-to-noise ratio of the signals is effectively improved.

In one embodiment, as shown in fig. 4, another embodiment of the present application provides a pulse lidar detection method, which includes the following steps 402 to 418. Wherein:

Step 402, the laser is controlled to output continuous laser light.

Step 404, receiving the continuous laser light by the second beam splitter and dividing the continuous laser light into a first continuous laser light and a second continuous laser light.

Step 406, receiving the first continuous laser and the circulating light through the first coupler, and coupling the first continuous laser and the circulating light into first coupled light and outputting the first coupled light.

In step 408, the modulator receives the first coupled light output by the first coupler, and performs frequency modulation and pulse modulation on the first coupled light to obtain first modulated light.

In step 410, a first beam splitter with a beam splitting ratio between 1:1 and 9:1 is used to receive the first modulated light, and the first modulated light is split to obtain light to be recycled and second modulated light, wherein the ratio of the light to be recycled to the second modulated light corresponds to the beam splitting ratio of the first beam splitter.

Step 412, receiving the light to be recycled through the optical amplifier to obtain recycled light, amplifying and delaying the recycled light, and transmitting the recycled light to the first coupler; wherein the recycled light comprises at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one modulated optical signal at least one time the modulation frequency shift.

In step 414, the processing module receives the second modulated light, emits the second modulated light onto the target to be measured, and receives the echo signal reflected back by the target to be measured.

Step 416, coupling the echo signal and the second continuous laser light through a second coupler to obtain a coupled optical signal.

In step 418, the detector receives the coupled optical signal, beats the coupled optical signal, and converts the beaten coupled optical signal into an electrical signal.

According to the pulse laser radar detection method, the first continuous laser and the circulating light are coupled into the first coupling light and then output to the modulator, the modulator carries out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light, and the first modulated light is split by the first beam splitter to obtain light to be circulated and second modulated light; converting light to be recycled into recycled light by using a recycling module, transmitting the recycled light to a first coupler, and adding extinction and frequency shift once for each modulation; thus, the more the number of modulations, the greater the frequency shift and extinction ratio, and in the frequency domain the greater the frequency shift and the higher the extinction ratio, the frequency can be selected according to the extinction ratio desired by the system, wherein the recycled light comprises at least one modulated optical signal having an extinction ratio at least one times the modulation extinction ratio and at least one times the frequency shift of the modulation. The application replaces the modulation mode of cascade connection of a plurality of modulators by a cyclic modulation mode, namely, the pulse with high extinction ratio can be obtained without cascading a plurality of modulators; the pulse laser radar detection method provided by the embodiment has less error sources and reduced adjustment complexity because of less adjustment parameters; the pulse laser radar detection method of the embodiment adopts the same modulator to circularly modulate when pulse modulation and frequency modulation are carried out, so that the uncertainty of a test result is reduced; furthermore, multimodal detection can be realized by selecting a plurality of frequencies, so that the error of unimodal detection can be reduced; that is, multimodal probing can improve measurement accuracy.

It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (10)

1. A pulsed lidar, the lidar comprising:

the laser module is used for outputting first continuous laser and second continuous laser;

the first coupler is used for receiving the first continuous laser and the circulating light, coupling the first continuous laser and the circulating light into first coupled light and outputting the first coupled light;

The modulator is used for receiving the first coupling light output by the first coupler, and carrying out frequency modulation and pulse modulation on the first coupling light to obtain first modulated light;

the first beam splitter is used for receiving the first modulated light and splitting the first modulated light to obtain light to be recycled and second modulated light;

The circulating module is used for receiving the light to be circulated, converting the light to be circulated into circulating light and transmitting the circulating light to the first coupler;

The processing module is used for receiving the second modulated light, transmitting the second modulated light to the target to be detected and receiving echo signals reflected back by the target to be detected;

and the detection module is used for converting the echo signal and the second continuous laser into electric signals after coupling.

2. The pulsed lidar of claim 1, wherein the circulation module comprises:

And the optical amplifier is used for receiving the light to be circulated to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

3. The pulsed lidar of claim 1 or 2, wherein the circulating light comprises at least one beam of modulated optical signal having an extinction ratio at least one times the modulation extinction ratio, and wherein the at least one beam of modulated optical signal has a frequency shift at least one time the modulation frequency shift.

4. The pulsed lidar according to claim 1 or 2, wherein the splitting ratio of the first beam splitter is between 1:1 and 9:1.

5. The pulsed lidar of claim 1, wherein the detection module comprises:

The second coupler is used for coupling the echo signal and the second continuous laser to obtain a coupled optical signal;

and the detector receives the coupling optical signals, beats the coupling optical signals, and converts the beaten coupling optical signals into electric signals.

6. A method of pulsed lidar detection, the method comprising:

controlling the laser module to output first continuous laser and second continuous laser;

Receiving the first continuous laser and the circulating light through a first coupler, coupling the first continuous laser and the circulating light into first coupled light, and outputting the first coupled light;

Receiving the first coupling light output by the first coupler through a modulator, and performing frequency modulation and pulse modulation on the first coupling light to obtain first modulated light;

Receiving first modulated light by a first beam splitter, and splitting the first modulated light to obtain light to be recycled and second modulated light;

Receiving the light to be circulated through a circulation module, converting the light to be circulated into circulating light and transmitting the circulating light to the first coupler;

receiving second modulated light through a processing module, transmitting the second modulated light to a target to be detected, and receiving echo signals reflected back by the target to be detected;

And coupling the echo signal and the second continuous laser through a detection module, and converting the coupled echo signal and the second continuous laser into an electric signal.

7. The method of claim 6, wherein the receiving the light to be recycled by a recycling module, converting the light to be recycled into recycled light for transmission to the first coupler comprises:

and receiving the light to be circulated through an optical amplifier to obtain circulated light, amplifying the circulated light, delaying the circulated light and transmitting the amplified circulated light to the first coupler.

8. The method of claim 6 or 7, wherein the recycled light comprises at least one beam of modulated light signal having an extinction ratio at least one times the modulation extinction ratio and a frequency shift of the at least one beam of modulated light signal at least one times the modulation frequency shift.

9. The method of claim 6, wherein receiving the first modulated light with a first beam splitter and splitting the first modulated light to obtain the light to be recycled and the second modulated light comprises:

and receiving the first modulated light by using a first beam splitter with the light splitting ratio of 1:1 to 9:1, and splitting the first modulated light to obtain light to be recycled and second modulated light, wherein the ratio of the light to be recycled to the second modulated light corresponds to the light splitting ratio of the first beam splitter.

10. The method of claim 6, wherein the coupling the echo signal and the second continuous laser light through the detection module to convert to an electrical signal comprises:

Coupling the echo signal and the second continuous laser through a second coupler to obtain a coupled optical signal;

And receiving the coupling optical signal through a detector, beating the coupling optical signal, and converting the coupling optical signal after beating into an electric signal.