CN113608228B - Quick scanning device and method for two-dimensional multi-beam laser radar based on blast matrix - Google Patents
Quick scanning device and method for two-dimensional multi-beam laser radar based on blast matrix Download PDFInfo
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Abstract
The invention discloses a two-dimensional multi-beam laser radar rapid scanning device and method based on a blast matrix. The tunable laser source array is utilized to generate a plurality of paths of mutually incoherent optical signals, the phase shifters in the blast matrix are controlled to adjust the phases of the plurality of paths of incoherent optical signals according to the preset beam directions, each path of optical signals reaches each antenna unit to have a specific phase difference, an optical phased array is formed, and scanning on the parallel dimension with the plane of the antenna array is realized. Since the diffraction grating is etched at the end face of the antenna unit waveguide, the diffraction angle of the diffraction grating is related to the wavelength of the optical signal, the scanning in the vertical dimension with the plane of the antenna array can be realized by adjusting the central wavelength of the laser, and the rapid scanning in two dimensions is realized. In addition, the invention has the advantages of compact structure, easy integration, flexible expansion of the number of beams and the like, and can meet various application requirements.
Description
Technical Field
The invention provides a two-dimensional multi-beam laser radar rapid scanning device and method based on a blast matrix, which are oriented to the requirements of rapid scene scanning laser radar in the field of radar detection and imaging.
Background
With the rapid development of technologies such as automatic driving, bridge collision avoidance, space meeting and docking and the like, further improving the ranging capability, imaging precision and speed of the radar are important trends. The traditional microwave imaging radar has the problems of larger system volume, wide antenna beam angle, longer imaging time and the like, and is more limited in the future more complex application environment. The laser radar with the rapid ranging and high-resolution imaging capability becomes an excellent choice for the application scene.
The existing laser radar ranging technology mainly comprises single-beam scanning ranging, and scanning in two dimensions is achieved by respectively adjusting the phase of light waves and the wavelength of the light waves. Although fast scanning imaging can also be achieved by control through external circuitry, with complex changes in the environment, new requirements are placed on radar ranging and scanning imaging speeds. In this regard, multi-beam simultaneous scanning lidar is becoming a recent trend. Recently, a method for rapidly scanning laser radar multi-beam based on a Butler matrix is proposed, but in the scheme, the Butler matrix can only meet the limit of a fixed scanning angle, and a first-stage phase shifter is added after the Butler matrix to realize the angle scanning within a certain range, which clearly increases the complexity of the system.
In conclusion, the existing laser radar has the problems of ranging, low imaging scanning speed, limited scanning angle and the like.
Disclosure of Invention
In order to overcome the defects of the conventional laser radar ranging and imaging method, the invention discloses a two-dimensional multi-beam laser radar rapid scanning device and method based on a blast matrix.
The technical scheme of the invention is as follows: a two-dimensional multi-beam laser radar rapid scanning device based on a blast matrix comprises: the system comprises a tunable laser source array unit, a multi-beam forming unit, an optical phased array antenna unit, a signal receiving and processing unit and a laser control unit; wherein,,
the tunable laser source array unit comprises a plurality of tunable lasers for generating a plurality of continuous light wave signals OS which have the same wavelength and can be tuned simultaneously and are mutually incoherent in phase 1 ，OS 2 ，...，OS M The number of the tunable lasers is equal to the number M of laser beam directors which are preset and scanned simultaneously;
the multi-beam forming unit: used for respectively shaping the amplitude and the phase of M paths of incoherent optical signals generated by the laser source array, adjusting the signal power transmitted to N antenna subunits in the optical antenna array and the phase difference value between adjacent antenna subunits according to the preset laser beam direction corresponding to each path of optical signals, finally, the M paths of incoherent optical signals are respectively split and shaped and are transmitted to the optical phased array antenna unit;
the optical phased array antenna unit: transmitting the optical signals with the fixed phase difference output by the multi-beam forming unit to form beams with the directions corresponding to the fixed phase difference values, receiving the optical wave signals reflected by the targets and then transmitting the optical wave signals to a subsequent signal processing unit; in addition, a diffraction grating is added to the emission port of each optical antenna unit, so that the output laser beam scans in the other dimension;
a signal reception processing unit: the optical signal reflected by the target is subjected to beam splitting and direction receiving, and is sent to a photoelectric detector for photoelectric conversion after being combined with a light source signal corresponding to the direction, and then is converted into a digital domain for subsequent signal processing through low-speed sampling;
and a laser control unit: the device is used for controlling the pumping current of the laser so as to adjust the wavelength of the laser output light according to the scanning angle requirement; and the device is also used for controlling the power and the phase of the optical signals output by each path in the multi-beam forming unit so as to realize the power required by the corresponding beam direction and the phase difference between adjacent antenna subunits, thereby realizing the simultaneous scanning of a plurality of different beam directions.
Further, the tunable laser source array unit comprises M tunable lasers for generating M incoherent optical signals with the same wavelength.
Further, the multi-beam forming unit comprises m×n MZI structures, each MZI structure for controlling power of each signal transmitted to the optical antenna; each MZI structure comprises two 3-dB couplers and 1 phase shifter, wherein one end output of the first 3-dB coupler is connected with one input end of the second 3-dB coupler through the phase shifter; the other end output of the first 3-dB coupler is directly connected to the other input of the second 3-dB coupler.
Further, the multi-beam forming unit comprises 2×m×n phase shifters, including m×n phase shifters on a trunk and phase shifters in upper branches of m×n MZI structures, where the phase shifters on the trunk are used to control phase differences required by different light beams to direct corresponding optical signals, and the phase shifters of the upper branches of the MZI structures are used for power of signals transmitted to the optical antennas in each path;
further, the optical phased array antenna unit includes: n optical waveguides engraved with diffraction gratings at the front end are used as optical antennas for realizing the transmission and the reception of optical wave signals of specific beam pointing directions;
further, the signal receiving and processing unit includes: m circulators are used for outputting the received optical signals to subsequent processing equipment along the 3 ports of the circulators, so as to avoid aliasing with the transmitted optical signals;
2×m optical couplers for splitting the light source signal, and for combining the light source signal and the received target reflected light signal;
and M Photodetectors (PD) for beating the light source signal and the received target reflected light signal.
Further, the digital sampling and processing module is used for digitally sampling the beat frequency signal output by the photoelectric detector and carrying out subsequent algorithm processing on the sampled signal to obtain the required target information;
further, the control unit includes: the laser temperature control module is used for controlling the temperature of the laser so that the laser can stably work for a long time;
the laser pumping current control module is used for controlling the laser to generate sweep frequency signals and can realize the adjustment of the light wavelength by adjusting the pumping current of the laser;
the phase shifter phase shift control module is used for controlling the power and the phase difference of different optical antenna subunits and realizing the functions of different directions and scanning of light beams;
according to another aspect of the present invention, a two-dimensional multi-beam laser radar fast scanning method based on a blast matrix is also provided, which comprises the following steps:
in the tunable laser source array unit, M laser sources simultaneously generate M paths of sweep light with the same central wavelength, sweep bandwidth and sweep period and incoherent sweep light by utilizing the laser control unit, and the sweep light is sent to the multi-beam forming unit through ports 1 to 2 of the circulator;
in the multi-beam forming unit, for the optical signal of the ith path, the combined action of the i-layer MZI structure and the phase shifter is needed, so when calculating the phase shift value of the phase shifter corresponding to the preset beam direction, the phase shifter of the first layer should be calculated from the first layer, after the phase shifter of the first layer can meet the phase shift value required by the first beam direction, the phase shift value of the phase shifter of the first layer is kept unchanged, the phase shift value of the phase shifter of the second layer is adjusted, and when calculating, the multi-path effect introduced by the multi-layer MZI structure is additionally considered, for example, the light emitted from the laser 2 reaches the second optical antenna unit, two paths can be taken, one is MZI 2，1 →MZI 1，1 →MZI 1，2 Another path is MZI 2，1 →MZI 2，2 →MZI 1，2 . Thus, the optical signals on the two paths may be subjected to different phase shifts and then subjected to MZI 1，2 The coherent superposition is realized, and finally, the combined beam is formed into one path of optical signal to be radiated at the optical antenna unit 2, and the like. Multipath effects are therefore necessarily present when calculating the phase shifter phase shift values for the multiple beam orientations. On the basis of considering the multipath effect, after phase shift values corresponding to the phase shifters from the first layer to the M layer are calculated in sequence, the phase shift values are reversely pushed to current values required to be provided for the phase shifters according to a carrier control scheme determined before, so that the phase shifters can be controlled by a control unit, and finally preset beam pointing scanning is realized;
in the optical phased array antenna unit, the N optical waveguides with the same diffraction grating at the front end carry out adjustment of the beam direction on the dimension perpendicular to the plane of the optical antenna array on the optical signals with the M paths of the optical signals after the power and the phase adjustment, and as for a specific diffraction grating, the angle of the beam diffracted by the optical waves after passing through the grating changes along with the change of the wavelength of the optical waves, the pumping current of the M lasers can be simultaneously adjusted through the control unit, so that the central wavelength of the M paths of the optical signals is simultaneously changed, and the scanning of the beam on the dimension perpendicular to the plane of the optical antenna array is realized;
in the signal receiving and processing unit, after the optical signals received by the optical phased array antenna array pass through the multi-beam forming unit, the target reflected signals pointed by different beams are separated into M paths, and are respectively coupled with corresponding initial light source signals after being output through the 2 to 3 ports of the circulator and sent into the photoelectric detector to perform photoelectric conversion.
The beneficial effects are that:
(1) By utilizing the structural advantage of a blast matrix, the invention provides an adaptive optical topological structure based on a blast matrix architecture, and realizes the rapid two-dimensional scanning of laser beams. The blast matrix is mainly applied to an electrical phased array originally, and one-dimensional scanning of microwave beams is achieved. The invention focuses the two-dimensional scanning of the laser beam, can realize the simultaneous emission or receiving of the signals of the laser beams in a plurality of directions, the number of the beams and the number of the antennas can be arbitrarily expanded, and the scanning of any beam angle can be realized in a very large angle range, thereby greatly improving the scanning speed of the laser radar and being beneficial to rapidly carrying out ranging and scanning imaging on specific targets.
(2) The scheme can be combined with compressed sensing, if the scene is in a sparse state, the direction of each wave beam can be selected according to specific scene requirements, so that the scanning time can be greatly reduced on the premise of ensuring that important information is not lost, and the performance of the system is improved.
(3) The device has a more compact structure, is beneficial to realizing the integration of a system on a chip and is also beneficial to large-scale expansion.
Drawings
FIG. 1 is a schematic diagram of a two-dimensional multi-beam laser radar fast scanning device based on a blast matrix;
fig. 2 is a detailed structure of the MZI in the multi-beam forming unit.
Detailed Description
The present invention will be further described in detail with reference to fig. 1 and the specific embodiment, in order to make the objects, technical solutions and advantages of the present invention more apparent.
The invention provides a two-dimensional multi-beam laser radar rapid scanning device based on a blast matrix, which comprises: the system comprises a tunable laser source array unit, a multi-beam forming unit, an optical phased array antenna unit, a signal receiving and processing unit and a laser control unit;
as shown in fig. 1, the device comprises M tunable lasers and laser control units with tunable wavelengths, M circulators, m×n MZI structures, 2×m×n phase shifters, N optical antenna units with the same diffraction grating, M photodetectors, and M analog-to-digital conversion modules.
Referring to fig. 1, a tunable laser source array unit (part I in fig. 1): for producing a plurality of simultaneously tunable, phase-incoherent continuous light wave signals OS of identical wavelength 1 ，OS 2 ，...，OS M . The number of the light sources is equal to the number M of the laser beam directors which are preset and scanned simultaneously.
Multibeam forming unit (section II in fig. 1): the method is used for respectively shaping the amplitude and the phase of M paths of incoherent optical signals generated by the laser source array, adjusting the signal power transmitted to N antenna subunits in the optical antenna array and the phase difference value between adjacent antenna subunits according to the preset laser beam directions corresponding to each path of optical signals, and finally realizing the respectively beam splitting and shaping of the M paths of incoherent optical signals and transmitting the M paths of incoherent optical signals to the optical phased array antenna unit.
Optical phased array antenna unit (section III in fig. 1): transmitting the optical signals with the fixed phase difference output by the multi-beam forming unit to form beams with the directions corresponding to the fixed phase difference values, receiving the optical wave signals reflected by the targets and then transmitting the optical wave signals to a subsequent signal processing unit; further, by adding a diffraction grating to each optical antenna element emission port, the output laser beam can be made to scan in another dimension.
Signal reception processing unit (section IV in fig. 1): the optical signal reflected by the target is received in a beam splitting direction, and is sent to the photoelectric detector for photoelectric conversion after being combined with the light source signal corresponding to the beam splitting direction, and then is converted into a digital domain for subsequent signal processing through low-speed sampling.
Laser control unit (V part in fig. 1): the device is used for controlling the pumping current of the laser so as to adjust the wavelength of the laser output light according to the scanning angle requirement; and the device is also used for controlling the power and the phase of the optical signals output by each path in the multi-beam forming unit so as to realize the power required by the corresponding beam direction and the phase difference between adjacent antenna subunits, thereby realizing the simultaneous scanning of a plurality of different beam directions.
The tunable laser source array unit comprises:
m tunable lasers for generating M incoherent optical signals having the same wavelength;
the multi-beam forming unit includes:
m×n MZI structures, each MZI structure as shown in fig. 2, for controlling power of each signal transmitted to the optical antenna;
2 xMxN phase shifters including MxN phase shifters on the trunk of FIG. 1 and phase shifters in the upper branches of the MxN MZI structures, the phase shifters on the trunk being used to control the phase difference required by different light beams to be directed to corresponding optical signals, the phase shifters of the upper branches of the MZI structures being used for the power of each signal to be transmitted to the optical antenna;
the optical phased array antenna unit comprises:
n optical waveguides engraved with diffraction gratings at the front end are used as optical antennas for realizing the transmission and the reception of optical wave signals of specific beam pointing directions;
the signal receiving and processing unit includes:
m circulators are used for outputting the received optical signals to subsequent processing equipment along the 3 ports of the circulators, so as to avoid aliasing with the transmitted optical signals;
2×m optical couplers for splitting the light source signal, and for combining the light source signal and the received target reflected light signal;
m Photodetectors (PDs) for beating the light source signal and the received target reflected light signal;
the digital sampling and processing module is used for digitally sampling the beat frequency signal output by the photoelectric detector and carrying out subsequent algorithm processing on the sampled signal to obtain the required target information;
the control unit includes:
the laser temperature control module is used for controlling the temperature of the laser so that the laser can stably work for a long time;
the laser pumping current control module is used for controlling the laser to generate sweep frequency signals and can realize the adjustment of the light wavelength by adjusting the pumping current of the laser;
the phase shifter phase shift control module is used for controlling the power and the phase difference of different optical antenna subunits and realizing the functions of different directions and scanning of light beams;
preferably, the phase shift amount control of the phase shifter selects carrier control. The phase shift amount control scheme of the phase shifter can be divided into three types of temperature control, current control and stress control, the tuning speed of the temperature control is slower, thermal crosstalk is easy to cause, and heat insulation treatment is needed additionally; the piezoelectric ceramic material is needed for stress control, and the tuning speed of the scheme is high, but the piezoelectric ceramic material is high in price and is more fragile in an actual working environment; in comparison, the tuning speed and cost of carrier control are more suitable.
Since the signal phase of each antenna subunit determines the final beam direction in the multi-beam forming process and the influence of the signal amplitude is small, the amplitude is ignored in the following deducing process, in the laser array module, by inputting the predistorted current signal to the laser control module, each laser outputs a signal with a center wavelength lambda 0 Swept optical signal O with gamma-modulated frequency 1 The steps of multi-beam forming are described as follows, with the 1-port entry circulator and 2-port output entry multi-beam forming unit:
first, the MZI structure in fig. 2 will be described: each MZI structure comprises two 3-dB couplers and 1 phase shifter, wherein one end output of the first 3-dB coupler is connected with one input end of the second 3-dB coupler through the phase shifter; the other end output of the first 3-dB coupler is directly connected to the other input end of the second 3-dB coupler; e_in1 and E_in2 are two input signals, E_out1 and E_out2 are two output signals, and the phase shift value of the phase shifter is set to phi, then the input/output signals of the MZI structure can be represented by the following formula:
where j is a complex unit. For simplicity, we let:
then equation (1) can be simplified to:
in the following derivation process, ein m，n And Eout m，n Separate table MZI m，n Input and output signals of r m，n And k m，n Then represent MZI m，n Is a coupling coefficient of ψ m，n Representation and MZI m，n Phase shift values of the phase shifters at corresponding positions.
The relationship between phase difference between adjacent antenna subunits and beam pointing is as follows:
where d is the distance between adjacent antenna subunits, θ is the beam pointing angle, and λ is the center wavelength of the optical signal.
First, for a first optical signal, i.e., a first beam θ 1 Since the first layer has no multipath effect, the method can be used as followsThe phase required for each antenna element is directly estimated according to equation (4) to thereby utilize the first layer phase shifter (ψ 1，1 ，ψ 1，2 ，...，Ψ 1，N ) Directly adjusting the phase difference of the optical signals on the N paths of antenna units;
second, calculate and adjust the second beam θ 2 The phase of each corresponding antenna subunit. The signal arriving at the antenna element 1 has no multipath effect and therefore the signal here can be expressed as:
E 2 refers to the beam emitted by the second laser; while there are two paths to the antenna unit 2, e.g. the light emitted from the laser 2 reaches the second optical antenna unit, there may be two paths to travel, one is MZI 2，1 →MZI 1，1 →MZI 1，2 Another path is MZI 2，1 →MZI 2，2 →MZI 1，2 . The signal can thus be expressed here as:
there are 3 paths to the antenna element 3, so here the signal can be expressed as:
by the method, the signal expression of the light pointed by each wave beam to the corresponding antenna sub-unit can be obtained, so that the phase shifter can be controlled to change the amplitude and the phase of the MZI output to realize the phase difference between the preset adjacent antenna sub-units and the corresponding wave beam pointing, and the phase shift value of the phase shifter can be continuously changed to change the pointing of each wave beam, thereby realizing scanning in the direction parallel to the plane of the antenna sub-units. Because the optical signals output by each laser are incoherent, the optical signals pointed by different beams are incoherent when reaching the antenna subunit, and the aliasing condition between the signals pointed by different beams can not occur.
The beam scanning in the direction perpendicular to the plane of the antenna unit is realized by diffracting optical signals with different wavelengths at different angles after passing through diffraction gratings at the waveguide ports of the optical antenna. The diffraction angle sigma of the light wave from the diffraction grating can be expressed by the following formula:
wherein lambda is the center wavelength of the optical signal, lambda is the grating constant, n eff Is the effective refractive index of the optical waveguide. As can be seen from the above, scanning in the dimension perpendicular to the plane of the optical antenna element can be achieved by shifting the center wavelength of the optical signal by varying the pumping currents of the M lasers.
Because the light path is reversible, the receiving process of the optical signal can be analogized with the signal transmitting process, under the same condition, the beam direction of the transmitted optical signal is completely consistent with the gain direction of the received optical signal, so that the optical signals reflected by different beam direction targets are redistributed after passing through the multi-beam forming units with the same parameters, and the signals with the same beam direction are distributed to the originally preset transmitting end channel, namely the corresponding beam direction is theta i The reflected optical signal of (2) passes through the multi-beam forming unit and returns to the optical path of the ith layer.
The following signal processing will be described by way of example, in which the optical signals from the light sources are incoherent and do not alias with each other, so that the optical signals from a single beam are directed. The light signal emitted by the light source can be expressed as:
E i ＝cos(2πft+πγt 2 +ψ 0 ) (8)
wherein f is the center frequency, gamma is the frequency of the sweep frequency, and ψ 0 For the initial phase, t is the time variable.
The signal received after the target is reflected and recombined and distributed by the multi-beam forming unit can be expressed as:
E i ＝cos[2πf(t-τ 0 -τ)+πγ(t-τ 0 -τ) 2 +ψ r ] (9)
wherein τ 0 For the delay from the tunable laser source unit to the optical antenna array unit, which is a fixed value, it can be measured in advance that τ is the delay from the antenna to the target, reflecting the relative position information of the target, ψ r For the phase of the received signal, generally, phi 0 Different.
The initial optical signal and the optical signal reflected by the target are combined and sent to the photoelectric detector to perform beat frequency through the coupler, and the generated beat frequency signal can be expressed as:
E PD ＝D.C.+H.F.+cos[2πγ(τ 0 +τ)t+2πf(τ 0 +τ)-πγ(τ 0 +τ) 2 +ψ 0 -ψ r ] (10)
wherein d.c. is a direct current component, h.f. is a high frequency component, which can be subsequently filtered by a band pass filter, and the frequency of the beat signal is a function of the amount of delay associated with the target distance, the target distance s can be extrapolated from the frequency of the signal:
wherein f PD The frequency of the beat signal, c is the propagation velocity of the electromagnetic wave.
Therefore, the distance information of the target in the corresponding beam direction can be extracted from the frequency information of the beat signal, and the whole information of the target can be obtained by carrying out beam scanning in two dimensions.
In summary, the invention utilizes the structural advantage of the blast matrix, can realize the simultaneous emission or reception of signals of laser beams in multiple directions, can expand the number of beams and the number of antennas at will, and can realize the scanning of any beam angle in a very large angle range, which greatly improves the scanning speed of the laser radar and is beneficial to the rapid ranging and scanning imaging of specific targets.
While the foregoing has been described in relation to illustrative embodiments thereof, so as to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but is to be construed as limited to the spirit and scope of the invention as defined and defined by the appended claims, as long as various changes are apparent to those skilled in the art, all within the scope of which the invention is defined by the appended claims.
Claims (10)
1. A two-dimensional multi-beam laser radar fast scanning device based on a blast matrix is characterized by comprising: the system comprises a tunable laser source array unit, a multi-beam forming unit, an optical phased array antenna unit, a signal receiving and processing unit and a laser control unit; wherein,,
the tunable laser source array unit comprises a plurality of tunable lasers for generating a plurality of continuous light wave signals OS which have the same wavelength and can be tuned simultaneously and are mutually incoherent in phase 1 ,OS 2 ,…,OS M The number of the tunable lasers is equal to the number M of laser beam directors which are preset and scanned simultaneously;
the multi-beam forming unit: used for respectively shaping the amplitude and the phase of M paths of incoherent optical signals generated by the laser source array, adjusting the signal power transmitted to N antenna subunits in the optical antenna array and the phase difference value between adjacent antenna subunits according to the preset laser beam direction corresponding to each path of optical signals, finally, the M paths of incoherent optical signals are respectively split and shaped and are transmitted to the optical phased array antenna unit;
the optical phased array antenna unit: transmitting the optical signals with the fixed phase difference output by the multi-beam forming unit to form beams with the directions corresponding to the fixed phase difference values, receiving the optical wave signals reflected by the targets and then transmitting the optical wave signals to a subsequent signal processing unit; in addition, a diffraction grating is added to the emission port of each optical antenna unit, so that the output laser beam scans in the other dimension;
a signal reception processing unit: the optical signal reflected by the target is subjected to beam splitting and direction receiving, and is sent to a photoelectric detector for photoelectric conversion after being combined with a light source signal corresponding to the direction, and then is converted into a digital domain for subsequent signal processing through low-speed sampling;
and a laser control unit: the device is used for controlling the pumping current of the laser so as to adjust the wavelength of the laser output light according to the scanning angle requirement; and the device is also used for controlling the power and the phase of the optical signals output by each path in the multi-beam forming unit so as to realize the power required by the corresponding beam direction and the phase difference between adjacent antenna subunits, thereby realizing the simultaneous scanning of a plurality of different beam directions.
2. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the tunable laser source array unit comprises M tunable lasers and is used for generating M incoherent optical signals with the same wavelength.
3. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the multi-beam forming unit comprises M x N Mach-Zehnder interference (MZI) structures, wherein each MZI structure is used for controlling the power of each signal transmitted to the optical antenna; each MZI structure comprises two 3-dB couplers and 1 phase shifter, wherein one end output of the first 3-dB coupler is connected with one input end of the second 3-dB coupler through the phase shifter; the other end output of the first 3-dB coupler is directly connected to the other input of the second 3-dB coupler.
4. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the multi-beam forming unit comprises 2×m×n phase shifters, including m×n phase shifters on a trunk and phase shifters in upper branches of m×n MZI structures, the phase shifters on the trunk are used for controlling phase differences required by different light beams to direct corresponding optical signals, and the phase shifters of the upper branches of the MZI structures are used for power of signals transmitted to the optical antennas per path.
5. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the optical phased array antenna unit comprises: n optical waveguides with diffraction grating carved on front end are used as optical antenna to realize the transmission and reception of light wave signal with specific beam pointing direction.
6. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the signal receiving and processing unit includes: m circulators are used for outputting the received optical signals to subsequent processing equipment along the 3 ports of the circulators, so as to avoid aliasing with the transmitted optical signals;
2×m optical couplers for splitting the light source signal, and for combining the light source signal and the received target reflected light signal;
and M Photodetectors (PD) for beating the light source signal and the received target reflected light signal.
7. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the digital sampling and processing module is used for digitally sampling the beat frequency signal output by the photoelectric detector and carrying out subsequent algorithm processing on the sampled signal to obtain the required target information.
8. The two-dimensional multi-beam laser radar rapid scanning device based on blast matrix according to claim 1, wherein the device comprises:
the control unit includes: the laser temperature control module is used for controlling the temperature of the laser so that the laser can stably work for a long time;
the laser pumping current control module is used for controlling the laser to generate sweep frequency signals and can realize the adjustment of the light wavelength by adjusting the pumping current of the laser;
and the phase shifter phase shift control module is used for controlling the power and the phase difference of different optical antenna subunits and realizing the functions of different directions and scanning of light beams.
9. A two-dimensional multi-beam laser radar rapid scanning method based on a blast matrix is characterized by comprising the following steps:
in the tunable laser source array unit, M laser sources simultaneously generate M paths of sweep light with the same central wavelength, sweep bandwidth and sweep period and incoherent sweep light by utilizing the laser control unit, and the sweep light is sent to the multi-beam forming unit through ports 1 to 2 of the circulator;
in the multi-beam forming unit, for the optical signal of the ith path, through the combined action of the i-layer MZI structure and the phase shifter, when calculating the phase shift value of the phase shifter corresponding to the preset beam direction, the phase shifter of the first layer is calculated from the first layer, after the phase shifter of the first layer can meet the phase shift value required by the first beam direction, the phase shift value of the phase shifter of the first layer is kept unchanged, and then the phase shift value of the phase shifter of the second layer is adjusted, and during calculation, the multipath effect introduced by the multi-layer MZI structure is additionally considered, so that the optical signals on two paths can be subjected to different phase shifts and then are subjected to MZI 1,2 Realizing coherent superposition, finally combining the beams into one path of optical signals to radiate at the optical antenna unit, and so on;
on the basis of considering the multipath effect, after the phase shift values corresponding to the phase shifters from the first layer to the M layer are calculated in sequence, the phase shift values are reversely pushed to the current values required to be provided for the phase shifters according to the carrier control scheme determined before, so that the phase shifters can be controlled by the control unit, and finally the preset beam pointing scanning is realized.
10. The two-dimensional multi-beam laser radar fast scanning method based on blast matrix according to claim 9, further comprising the steps of:
in the optical phased array antenna unit, N optical waveguides with the same diffraction grating at the front end carry out adjustment of beam direction on the dimension perpendicular to the plane of the optical antenna array on the optical signals with the power and the phase adjusted on the M paths, and the pump currents of the M lasers are adjusted simultaneously through the control unit, so that the central wavelength of the M paths of optical signals is changed simultaneously, and the scanning of the optical beams on the dimension perpendicular to the plane of the optical antenna array is realized;
in the signal receiving and processing unit, after the optical signals received by the optical phased array antenna array pass through the multi-beam forming unit, target reflection signals pointed by different beams are separated into M paths, the M paths are respectively coupled with corresponding initial light source signals after being output through the 2 to 3 ports of the circulator, the signals are sent into the photoelectric detector to perform photoelectric conversion, the frequency of the beat frequency generation signals is related to the target distance in the direction pointed by the corresponding beams, and the related information about the target can be obtained by sampling and processing the beat frequency signals.
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