CN111239754A - Laser radar system based on frequency-adjustable continuous wave and imaging method thereof - Google Patents
Laser radar system based on frequency-adjustable continuous wave and imaging method thereof Download PDFInfo
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- CN111239754A CN111239754A CN202010059300.2A CN202010059300A CN111239754A CN 111239754 A CN111239754 A CN 111239754A CN 202010059300 A CN202010059300 A CN 202010059300A CN 111239754 A CN111239754 A CN 111239754A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres
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- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
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- Optical Radar Systems And Details Thereof (AREA)
Abstract
A laser radar system based on frequency-adjustable continuous waves and an imaging method thereof belong to the technical field of laser radars. The problems of interference, poor compensation effect, complex iterative operation and low speed in the conventional distance measurement method are solved. The technical points are as follows: the arbitrary waveform generator, the amplifier and the modulator are connected in sequence, the laser, the first polarization controller and the modulator are connected in sequence, the first optical fiber circulator is respectively connected with the electro-optical modulator, the DFB laser and the first optical fiber coupler, one path of the first optical fiber coupler is connected with the second polarization controller and the second optical fiber coupler, the other path of the first optical fiber coupler is connected with the second optical fiber circulator and the collimator, the second optical fiber circulator is connected with the second optical fiber coupler and the detector, the two-dimensional scanning galvanometer is installed at the emergent end of the collimator, and the data acquisition card is connected with the two-dimensional scanning galvanometer, the arbitrary waveform generator and the detector. The invention adopts a laser external modulation mode to realize the rapid linear frequency modulation of the light source, and is used for a laser radar system to realize three-dimensional imaging.
Description
Technical Field
The invention relates to a laser radar system and an imaging method thereof, in particular to a laser radar system based on frequency-adjustable continuous waves and an imaging method thereof, and belongs to the technical field of laser radars.
Background
The laser radar uses laser as a light source, and adopts a photoelectric detection technology to realize active detection equipment for the target distance. The method has the advantages of high precision, high speed, small size and the like, and is widely applied to the fields of automatic driving, unmanned aerial vehicles, intelligent robots, three-dimensional modeling, geographical mapping and the like.
The current laser radar is mainly classified into a time of flight (TOF) ranging method and a Frequency Modulated Continuous Wave (FMCW) ranging method. The distance is directly measured by detecting the round trip time of the pulse light reflected from the light source to the detector through the object surface, the method has a simple structure, but is seriously interfered by background light, interference exists among radars, and the used light source is harmful to human eyes. The latter indirectly measures the distance by detecting the beat frequency signal between the reference light and the signal light reflected by the object surface, and the method has the advantages of strong anti-interference capability, safety to human eyes and the like, but has strict requirements on the frequency modulation linearity of the light source, because the non-linearity of the frequency modulation can seriously affect the measurement precision. Aiming at the problem of frequency modulation linearity, the method adopts an auxiliary interferometer which is a common method and can convert equal time interval sampling into equal frequency interval sampling so as to compensate the nonlinearity of light source frequency modulation, but the method belongs to an approximate algorithm and has poor compensation effect under the condition of long measurement distance. The other method is to internally modulate the light source through a pre-iterative algorithm so that the light source outputs a frequency modulation continuous wave with high linearity, but the method needs a large amount of iterative calculation, and in addition, the laser internal modulation method also has the defect of low frequency modulation speed and is not beneficial to the rapid measurement of the laser radar.
The FMCW based ranging principle is as follows:
it is assumed that the change in the reference light frequency with time can be expressed as: f. ofLO(t)＝kt+f0. Where k is the frequency modulation speed, f0Is the initial frequency.
The round-trip time of the signal light from the collimator to the measured object is Δ t, and the change of the frequency of the signal light with time can be expressed as: f. ofSignal(t)＝k(t+Δt)+f0。
The difference frequency signal of the reference light and the signal light detected by the detector can be expressed as: Δ f ═ k Δ t.
The target distance can be expressed as:
where c is the speed of light.
When the frequency modulation speed k is known, the acquired signal is subjected to FFT operation to obtain delta f, so that distance information is obtained.
Disclosure of Invention
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to determine the key or critical elements of the present invention, nor is it intended to limit the scope of the present invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
In view of the above, in order to solve the problems of interference and harm to human eyes in the existing TOF ranging method and the problems of poor compensation effect, complex iterative operation and low speed in the FMCW ranging method, the invention further designs a laser radar system based on frequency-adjustable continuous waves and an imaging method thereof, wherein the laser radar system adopts an external laser modulation mode to realize rapid linear frequency modulation of a light source and is used for the laser radar system to realize three-dimensional imaging.
The first scheme is as follows: the invention provides a frequency-adjustable continuous wave-based laser radar system, which comprises a narrow-linewidth laser, an electro-optic modulator, an arbitrary waveform generator, a microwave amplifier, a DFB laser, an optical fiber collimator, a two-dimensional scanning galvanometer, a photoelectric detector, a data acquisition card, a first polarization controller, a second polarization controller, a first optical fiber circulator, a second optical fiber circulator, a first optical fiber coupler and a second optical fiber coupler, wherein the narrow-linewidth laser is connected with the optical fiber modulator through the first optical fiber circulator;
the waveform output port of the arbitrary waveform generator is connected with the input port of a microwave amplifier, the output port of the microwave amplifier is connected with the microwave signal input port of an electro-optical modulator, the output port of a narrow-linewidth laser is connected with the optical signal input port of the electro-optical modulator through a first polarization controller, the optical output port of the electro-optical modulator is connected with the I port of a first optical fiber circulator, the output port of a DFB laser is connected with the II port of a first optical fiber circulator, the III port of the first optical fiber circulator is connected with a first optical fiber coupler, the I output port of the first optical fiber coupler is connected with a second optical fiber coupler through a second polarization controller, the II output port of the first optical fiber coupler is connected with the I port of a second optical fiber circulator, the II port of the second optical fiber circulator is connected with an optical fiber collimator, and the III port of the second optical fiber circulator is connected with a second; the output port of the second optical fiber coupler is connected with the optical signal input of the photoelectric detector, the two-dimensional scanning galvanometer is installed in the emergent light beam direction of the optical fiber collimator, and the data acquisition card is simultaneously connected with the two-dimensional scanning galvanometer, the arbitrary waveform generator and the photoelectric detector.
Further: the electrical signal output port of the optical fiber detector is connected to a first acquisition channel of the data acquisition card, the two-dimensional position electrical signal of the two-dimensional scanning galvanometer is connected to a second acquisition channel of the data acquisition card, and the trigger signal output by the arbitrary waveform generator is connected to an external trigger channel of the data acquisition card.
Further: the line width of the narrow line width laser is less than 10 kHz.
Further: the central wavelengths of the narrow linewidth laser and the DFB laser are adjustable near 1550nm, and the narrow linewidth laser and the DFB laser have wavelength overlapping ranges.
Further: the bandwidths of the electro-optical modulator, the arbitrary waveform generator and the microwave amplifier are all larger than 15 GHz.
Further: the DFB laser is free of optical isolators to achieve injection locking.
Further: the aperture of the optical fiber collimator is larger than or equal to 1 inch, so that the system can receive optical signals reflected by an object by using the optical fiber collimator after emitting laser, and the function of simultaneous receiving and transmitting is achieved.
Further: the photoelectric detector is a balanced detector and has the bandwidth of 100 MHz.
Further: the first optical fiber coupler and the second optical fiber coupler are both 1 × 2 or 2 × 2 ports.
Scheme II: the invention provides a laser radar imaging method based on frequency-adjustable continuous waves, which is realized based on a laser radar system in the first scheme. The method specifically comprises the following steps:
the method comprises the following steps that an arbitrary waveform generator generates a linear frequency modulation microwave signal and loads the linear frequency modulation microwave signal to an electro-optic modulator through a microwave amplifier, light emitted by a narrow-linewidth laser is modulated through the electro-optic modulator to generate a first-order sideband, direct-current bias voltage of the electro-optic modulator is adjusted to enable the carrier suppression ratio to be maximum, a first polarization controller is adjusted to enable the intensity of the first-order sideband to be maximum, and the wavelength of a DFB laser is adjusted to enable the wavelength of the DFB laser to be equal to the central wavelength; through an injection locking technology, light output by the first optical fiber circulator is linear frequency modulation continuous light;
the first optical fiber coupler divides the output linear frequency modulation continuous light into two paths, wherein one path of light enters the second optical fiber coupler as reference light through the second polarization controller, the other path of light enters the optical fiber collimator as signal light through the second optical fiber circulator and irradiates the surface of a measured object, the light reflected by the measured object is received by the optical fiber collimator and enters the second optical fiber coupler through the second optical fiber circulator to generate frequency mixing with the reference light to generate a beat frequency signal, and the second polarization controller is adjusted to enable the intensity of the beat frequency signal to be maximum; the generated beat frequency signal is detected by the photoelectric detector and is collected by the data acquisition card for subsequent processing;
the two-dimensional scanning of the measured object is realized by changing the direction of the light beam emitted by the optical fiber collimator through the two-dimensional scanning galvanometer; the direction signal of the two-dimensional scanning galvanometer and the beat frequency signal of the photoelectric detector are simultaneously acquired through the data acquisition card, and the distance information of two-dimensional points is obtained through data processing, so that the three-dimensional imaging of the measured object is realized.
Has the advantages that:
1. the laser external modulation method can realize the linear frequency modulation of the light source, does not need to compensate the nonlinearity of the light source frequency modulation, has the advantage of simple structure, and is easy for batch production and commercial application.
2. The method for laser external modulation can realize rapid frequency modulation of the light source, can acquire distance information of hundreds of thousands of measured points per second, and has great significance for rapid three-dimensional imaging.
3. The laser radar realized by the invention adopts a coherent detection technology, has the advantages of high signal-to-noise ratio and strong background light interference resistance, and the wavelength of the used light source is harmless to human eyes.
Drawings
FIG. 1 is a schematic diagram of a lidar system of the present invention;
FIG. 2 is a schematic diagram of FMCW-based ranging principles;
FIG. 3 is a graph of a chirped light spectrum implemented by an injection locking technique;
FIG. 4 is a graph of the demodulation result of the lidar of the present invention for a single point distance;
fig. 5 is a diagram of the three-dimensional imaging effect achieved by the lidar of the present invention.
In the figure, the devices are respectively: 1. a narrow linewidth laser; 2. an electro-optic modulator; 3. an arbitrary waveform generator; 4. a microwave amplifier; 5. a DFB laser; 6. a fiber collimator; 7. two-dimensional scanning galvanometer; 8. a photodetector; 9. a data acquisition card; 101. a first polarization controller; 102. a second polarization controller; 111. a first fiber optic circulator; 112. a second fiber circulator 121, a first fiber coupler; 122. a second fiber coupler.
Detailed Description
Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the device structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
Example 1: as shown in fig. 1, a laser radar system based on tunable continuous waves in this embodiment includes a narrow-linewidth laser 1, an electro-optic modulator 2, an arbitrary waveform generator 3, a microwave amplifier 4, a DFB laser 5, an optical fiber collimator 6, a two-dimensional scanning galvanometer 7, a photodetector 8, a data acquisition card 9, a first polarization controller 101, a second polarization controller 102, a first optical fiber circulator 111, a second optical fiber circulator 112, a first optical fiber coupler 121, and a second optical fiber coupler 122;
the waveform output port of the arbitrary waveform generator 3 is connected with the input port of the microwave amplifier 4, the output port of the microwave amplifier 4 is connected with the microwave signal input port of the electro-optical modulator 2, and the bandwidths of the electro-optical modulator 2, the arbitrary waveform generator 3 and the microwave amplifier 4 are all larger than 15 GHz; the line width of the narrow-line-width laser 1 is less than 10kHz, the output port of the narrow-line-width laser is connected with the optical signal input port of the electro-optical modulator 2 through the first polarization controller 101, the optical output port of the electro-optical modulator 2 is connected with the I port of the first optical fiber circulator 111, the output port of the DFB laser 5 is connected with the II port of the first optical fiber circulator 111, the III port of the first optical fiber circulator 111 is connected with the first optical fiber coupler 121, one output port of the first optical fiber coupler 121 is connected with the second optical fiber coupler 122 through the first polarization controller 101, and the other output port is connected with the I port of the second optical fiber circulator 112. The II port of the second optical fiber circulator 112 is connected with the optical fiber collimator 6, and the III port of the second optical fiber circulator 112 is connected with the second optical fiber coupler 122; the output port of the second optical fiber coupler 122 is connected with the optical signal input of the photoelectric detector 8, the two-dimensional scanning galvanometer 7 is installed in the direction of the light beam emitted by the optical fiber collimator 6, and the data acquisition card 9 is simultaneously connected with the two-dimensional scanning galvanometer 7, the arbitrary waveform generator 3 and the photoelectric detector 8.
Example 2, described with reference to fig. 1 to 5, example 2 is achieved by example 1. Firstly, writing a linear frequency-modulated waveform into an arbitrary waveform generator 3, setting the arbitrary waveform generator 3 to repeatedly output the waveform, and simultaneously outputting a trigger pulse signal along with the waveform to be connected to an external trigger channel of a data acquisition card 9. An arbitrary waveform generator 3 generates a chirp microwave signal and loads the chirp microwave signal to an electro-optic modulator 2 through a microwave amplifier 4, light emitted by a narrow linewidth laser 1 is modulated through the electro-optic modulator 2 to generate a first-order sideband, and a spectrometer is used for monitoring the modulated optical signal. The dc bias of the electro-optical modulator 2 is adjusted to maximize the carrier rejection ratio and the first polarisation controller 101 is adjusted to maximize the intensity of the first order sidebands. The wavelength of the DFB laser 5 is adjusted to be equal to the center wavelength of the first-order sidebands. By the injection locking technique, the light output from the first fiber circulator 111 is a chirped continuous light, and its spectrum in the frequency domain is shown in fig. 3.
The embodiment specifically measures the single-point distance as follows:
referring to fig. 1, the light output from the first fiber circulator 111 is divided into two paths by the first fiber coupler 121, wherein one path of light is used as a reference light to connect with the second polarization controller 102, and the frequency of the reference light changes with time as shown by a solid line in fig. 2. The other optical path is connected as a signal light to the I port of the second fiber optic circulator 112. The II port of the second optical fiber circulator 112 is connected with the optical fiber collimator 6; the III port of the second fiber circulator 112 is connected to a second fiber coupler 122. The light is emitted from the optical fiber collimator 6 and irradiated to the object to be measured, the light reflected by the object to be measured is received by the optical fiber collimator 6, and the change of the frequency of the signal light with time due to the time delay is shown by a dotted line in fig. 2. The reference light and the signal light are mixed in the second fiber coupler 122 to generate a beat signal having a frequency Δ f. The beat frequency signal is detected by the photoelectric detector 8 and collected by the data acquisition card 9, and the external trigger mode is selected. The second polarization controller 102 is adjusted to maximize the strength of the beat signal. And performing Fast Fourier Transform (FFT) on the acquired beat frequency signal to obtain a beat frequency delta f. Knowing the speed of light c and the frequency-modulated speed k of the light source, the distance to the target can be determined
The FFT spectrum of the beat signal is shown in fig. 4.
The three-dimensional imaging of the present embodiment is specifically as follows:
as described with reference to fig. 1, the light emitted from the fiber collimator 6 is redirected by the two-dimensional galvanometer 7 to be scanned in two dimensions. The position signals output by the two-dimensional galvanometer 7 are synchronously acquired by a data acquisition card 9. The distance information of each position on the two-dimensional plane is obtained through computer processing, and then the three-dimensional imaging of the measured object can be realized. Fig. 5 is a photomicrograph of a foam board and the three-dimensional imaging results achieved with the present invention.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The laser radar system based on the tunable continuous wave and the imaging method thereof provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (9)
1. A laser radar system based on frequency-adjustable continuous waves is characterized by comprising a narrow-linewidth laser (1), an electro-optic modulator (2), an arbitrary waveform generator (3), a microwave amplifier (4), a DFB laser (5), an optical fiber collimator (6), a two-dimensional scanning galvanometer (7), a photoelectric detector (8), a data acquisition card (9), a first polarization controller (101), a second polarization controller (102), a first optical fiber circulator (111), a second optical fiber circulator (112), a first optical fiber coupler (121) and a second optical fiber coupler (122);
the arbitrary waveform generator (3) generates a chirp microwave signal in a sawtooth waveform form, a waveform output port of the arbitrary waveform generator (3) is connected with an input port of a microwave amplifier (4), an output port of the microwave amplifier (4) is connected with a microwave signal input port of an electro-optical modulator (2), an output port of a narrow-linewidth laser (1) is connected with an optical signal input port of the electro-optical modulator (2) through a first polarization controller (101), an optical output port of the electro-optical modulator (2) is connected with an I port of a first optical fiber circulator (111), an output port of a DFB laser (5) is connected with an II port of the first optical fiber circulator (111), an III port of the first optical fiber circulator (111) is connected with a first optical fiber coupler (121), an I output port of the first optical fiber coupler (121) is connected with a second optical fiber coupler (122) through a second polarization controller (102), the II output port of the first optical fiber coupler (121) is connected with the I port of the second optical fiber circulator (112), the II port of the second optical fiber circulator (112) is connected with the optical fiber collimator (6), and the III port of the second optical fiber circulator (112) is connected with the second optical fiber coupler (122); an output port of the second optical fiber coupler (122) is connected with an optical signal input of the photoelectric detector (8), the two-dimensional scanning galvanometer (7) is installed in the direction of a light beam emitted by the optical fiber collimator (6), and the data acquisition card (9) is simultaneously connected with the two-dimensional scanning galvanometer (7), the arbitrary waveform generator (3) and the photoelectric detector (8).
2. The tunable continuous wave-based lidar system according to claim 1, wherein the electrical signal output port of the fiber-optic probe 8 is connected to a first acquisition channel of the data acquisition card (9), the two-dimensional position electrical signal of the two-dimensional scanning galvanometer (7) is connected to a second acquisition channel of the data acquisition card (9), and the trigger signal output by the arbitrary waveform generator (3) is connected to an external trigger channel of the data acquisition card (9).
3. A tuneable continuous wave-based lidar system according to claim 2, wherein the narrow linewidth laser (1) has a linewidth of less than 10 kHz.
4. The tunable continuous wave-based lidar system of claim 3, wherein the center wavelengths of the narrow linewidth laser (1) and the DFB laser (5) are tunable around 1550nm with a wavelength overlap range.
5. The frequency-modulated continuous wave-based lidar system according to any of claims 1 to 4, wherein the bandwidth of the electro-optical modulator (2), the arbitrary waveform generator (3), and the microwave amplifier (4) is greater than 15 GHz.
6. The tunable continuous wave-based lidar system of claim 1, wherein the DFB laser (5) does not include an optical isolator.
7. The tunable continuous wave-based lidar system of claim 6, wherein the photodetector (8) is a balanced detector with a bandwidth of 100 MHz.
8. The tunable continuous wave-based lidar system of claim 5, wherein the first fiber coupler (121) and the second fiber coupler (122) are each 1 x 2 or 2 x 2 ports.
9. A lidar imaging method based on tunable continuous waves, which is implemented based on the lidar system according to any of claims 1 to 8, and is characterized in that the lidar imaging method specifically comprises the following steps:
an arbitrary waveform generator (3) generates a sawtooth waveform type chirp microwave signal and loads the sawtooth waveform type chirp microwave signal to an electro-optic modulator (2) through a microwave amplifier (4), light emitted by a narrow linewidth laser (1) is modulated through the electro-optic modulator (2) to generate a first-order sideband, direct current bias of the electro-optic modulator (2) is adjusted to enable the carrier suppression ratio to be maximum, a first polarization controller (101) is adjusted to enable the intensity of the first-order sideband to be maximum, and the wavelength of a DFB laser (5) is adjusted to enable the wavelength of the DFB laser to be equal to the central wavelength of the first-order sideband; through an injection locking technology, light output by the first optical fiber circulator (111) is chirp continuous light;
the first optical fiber coupler (121) divides the output chirped continuous light into two paths, wherein one path of light enters the second optical fiber coupler (122) through the second polarization controller (102) as reference light, the other path of light enters the optical fiber collimator (6) through the second optical fiber circulator (112) as signal light and irradiates the surface of a measured object, the light reflected by the measured object is received by the optical fiber collimator (6) and enters the second optical fiber coupler (122) through the second optical fiber circulator (112) to generate frequency mixing with the reference light to generate a beat frequency signal, and the second polarization controller (102) is adjusted to enable the intensity of the beat frequency signal to be maximum; the photoelectric detector (8) detects the generated beat frequency signal and the beat frequency signal is collected by the data acquisition card (9) for subsequent processing;
the direction of the light beam emitted by the optical fiber collimator (6) is changed through the two-dimensional scanning galvanometer (7), so that the two-dimensional scanning of the measured object is realized; the direction signal of the two-dimensional scanning galvanometer (7) and the beat frequency signal of the photoelectric detector (8) are simultaneously collected through a data acquisition card (9), and the distance information of two-dimensional points is obtained through data processing, so that the three-dimensional imaging of the measured object is realized.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114563793A (en) * | 2022-03-02 | 2022-05-31 | Nano科技(北京)有限公司 | Distributed frequency modulation continuous wave laser radar |
| WO2022134136A1 (en) * | 2020-12-25 | 2022-06-30 | 北醒（北京）光子科技有限公司 | Frequency-modulated continuous-wave lidar system and lidar scanning method |
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