CN117538849A - Vortex laser-based spaceborne wide-field laser radar - Google Patents

Vortex laser-based spaceborne wide-field laser radar Download PDF

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Publication number
CN117538849A
CN117538849A CN202311296238.9A CN202311296238A CN117538849A CN 117538849 A CN117538849 A CN 117538849A CN 202311296238 A CN202311296238 A CN 202311296238A CN 117538849 A CN117538849 A CN 117538849A
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China
Prior art keywords
vortex
laser
target
vortex laser
field
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CN202311296238.9A
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Chinese (zh)
Inventor
张伟
赵艳彬
叶晖
刘阳
陈功轩
胡玲娜
倪涛
刘翠军
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Shanghai Institute of Satellite Engineering
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Shanghai Institute of Satellite Engineering
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Priority to CN202311296238.9A priority Critical patent/CN117538849A/en
Publication of CN117538849A publication Critical patent/CN117538849A/en
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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
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/4861—Circuits for detection, sampling, integration or read-out
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

The invention provides a vortex laser-based satellite-borne wide-field laser radar, which comprises: the device comprises a seed light source, a vortex modulator, a telescope, a vortex demodulator, a detector and a data processing unit; in a single scanning work flow, common Gaussian laser generated by a seed light source is changed into vortex laser after passing through a vortex modulator, an echo is generated after the vortex laser irradiates a target, the vortex laser is received by a telescope, demodulated by the vortex demodulator, enters a detector for imaging, and finally data processing is carried out. According to the invention, vortex laser is adopted as a carrier wave, the phase information of the echoes after being reflected by targets with different shapes shows a specialized morphological characteristic, and the shape type of an object contained in a single scanning is determined by analyzing the phase information in the echoes, so that the interference of non-target objects with the same type is eliminated. The method has the characteristics of good weak echo signal detection capability, large field angle, large laser footprint and high area coverage rate.

Description

Vortex laser-based spaceborne wide-field laser radar
Technical Field
The invention belongs to the field of spaceborne laser radars, and particularly relates to a vortex laser-based spaceborne wide-field laser radar.
Background
The laser radar can work all day long because of the self irradiation light source, is not limited by the day and night, and has the advantages of narrow carrier line width, high resolution and high sensitivity. The carrier wave of the laser radar contains information in various aspects such as amplitude, phase and frequency, and plays an increasing role in various fields such as radar imaging, wind measurement, greenhouse gas, atmospheric environment monitoring, underwater detection, deep space detection and the like.
The spaceborne laser radar is a laser radar loaded on a spacecraft and operates outside the earth atmosphere, has the unique advantages of all weather, small influence by the atmosphere, wide observation field of view and the like, and has the defects of weaker echo signals and smaller field of view due to the fact that the distance from a detection target is far.
The existing spaceborne laser radar mainly adopts the following two detection systems:
(1) Direct detection system
The satellite-borne laser radar adopting the direct detection system carries out detection by modulating the intensity of a laser signal, and is shown in figure 1. The laser transmitting end transmits the modulated laser pulse signal, and receives and processes the laser pulse echo signal at the receiving end. Because the satellite is far away from the ground (generally in the order of hundred kilometers), the echo signal of the satellite-borne laser radar is very weak, and the receiving end receives a large amount of noise signals while receiving the laser echo signal. Because the direct detection laser radar only uses the amplitude information of the laser carrier, the capability of suppressing background noise is limited, and the detection precision is lower.
(2) Coherent probe system
The satellite-borne laser radar adopting the coherent detection system not only modulates the laser signal intensity, but also modulates the laser signal phase, and the receiver strengthens the echo signal by using local oscillation laser, so that noise signals are suppressed, as shown in fig. 2. Compared with a direct detection system, the coherent detection system can improve the received signal to noise ratio and improve the detection capability of weak signals.
The satellite-borne laser radars of the two systems have the following problems:
(1) The laser angle of view and the diameter of the footprint are small, and the coverage performance is poor
The space-borne laser radar has certain advantages in the aspects of system performance such as acting distance, ranging precision and the like, but can only play a role under the condition of smaller transmitting and receiving fields of view due to factors such as background light interference and the like. With a fixed distance to the detection area, a small field angle inevitably results in limited lidar coverage performance, which will affect its ability to search for and capture targets.
The field angle and footprint size index of the existing spaceborne laser radar are shown in the following table:
TABLE 1 field angle, footprint size for existing spaceborne lidar
The table shows that the existing spaceborne laser radar has smaller field angle, smaller laser footprint size (hundred meters), can only work in a narrow field scanning mode when detecting a larger target area, and cannot perform wide field imaging with high imaging speed, no distance correction processing and clear targets.
(2) Weak echo signal with insufficient detection capability
As space-borne lidars find application in a wider range of fields, there is a need in some situations to detect objects that are farther apart, at greater speed, or that have a low reflectivity, which will cause the signal strength of the echo to be further reduced. Under the interference of strong background noise, the existing laser radar cannot realize the high-sensitivity active detection of the weak echo signals under the conditions. Even though the existing laser radar with highest sensitivity, the laser radar using the single photon detection technology has extremely harsh use conditions, is extremely susceptible to various noise including solar background noise and artificial interference noise, and cannot be applied in the daytime or in a complex environment.
In view of the foregoing, it is desirable to provide a novel satellite-borne laser radar with a wide field of view (a wide laser footprint size and a high coverage performance) and a strong weak echo signal detection capability, which has a strong wide field of view imaging capability and can detect a wide range.
Vortex laser is a special laser with unique spiral phase and orbital angular momentum characteristics. The light intensity of the common Gaussian laser in the section with the same propagation distance shows the distribution of strong center and weak center and the same phase, while the light intensity distribution of the vortex laser is annular and the phases in the section are not different. The vortex laser has two important parameters, namely radial quantum number and angular quantum number, wherein the radial quantum number influences the number of rings of the annular distribution of the plane light intensity of the vortex laser, and the angular quantum number influences the cycle number of plane phase change.
Due to the advantages of vortex lasers, the method has been used in the fields of particle manipulation, optical communication, microscopic imaging, quantum information, measuring the rotational momentum of objects and the like. However, no vortex laser application example applied to satellite remote sensing exists at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a vortex laser-based satellite-borne wide-field laser radar.
According to the invention, a vortex laser-based satellite-borne wide-field laser radar is loaded on a satellite and comprises: the device comprises a seed light source, a vortex modulator, a telescope, a vortex demodulator, a detector and a data processing unit;
the seed light source is used for generating Gaussian laser and transmitting the Gaussian laser to the vortex modulator;
the vortex modulator is used for modulating Gaussian laser into vortex laser;
the telescope is used for transmitting vortex laser and receiving echo light signals generated by the vortex laser reflected by the detection target;
the vortex demodulator is used for de-vortex the echo optical signal;
the detector is used for imaging the echo optical signals after the vortex is released;
the data processing unit is used for carrying out data processing according to imaging.
Preferably, the echo signals are resolved under the condition of low signal-to-noise ratio by utilizing the phase information contained in the vortex laser; wherein the low signal-to-noise condition includes a condition where the earth black body radiates and sunlight ground reflected light as background noise.
Preferably, vortex laser is adopted as carrier wave, phase information of echoes after reflection of different appearance targets presents specialized morphological characteristics, and appearance types of objects contained in a single scan are determined by analyzing the phase information in the echoes, so that interference of non-target same-category objects is eliminated.
Preferably, in a single scanning work flow, the common Gaussian laser generated by the seed light source is changed into vortex laser after passing through the vortex modulator, an echo is generated after the vortex laser irradiates a target, the vortex laser is received by the telescope, demodulated by the vortex demodulator, then enters the detector for imaging, and finally data processing is carried out.
Preferably, when capturing targets existing in the potential range of the targets, vortex laser radar is utilized to generate vortex laser, and a search strategy of sequential scanning column by column is adopted to search for the full coverage scanning in the range.
Preferably, vortex laser irradiates on the target to reflect and receive echo signals, and imaging and identification of the target are achieved in combination with the target type identification capability.
Preferably, a vortex laser annular light spot full coverage scanning strategy is adopted to scan to realize the full coverage of the area, and the following equation is adopted:
wherein d r Representing intra-column scan intervalsDistance, R represents the inner diameter of the light spot, R represents the outer diameter of the light spot, d c Representing the inter-column scan spacing.
The satellite provided by the invention comprises the vortex laser-based satellite-borne wide-field laser radar.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention utilizes vortex laser to carry out detection, has good weak echo signal detection capability, and simultaneously has the characteristics of large field angle, large laser footprint and high area coverage rate.
2. The invention uses the phase information contained in vortex laser to distinguish echo signals under the condition of low signal-to-noise ratio, especially under the condition that the blackbody radiation of the earth and the ground reflection light of sunlight are used as background noise.
3. The invention improves the detection signal-to-noise ratio, so that the detection field angle can be increased and the laser footprint size can be enlarged on the basis of meeting the detection signal-to-noise ratio index of the traditional laser radar.
4. The invention has the functions of imaging and positioning targets under a wide view field. Because of the high weak signal resolving power of the vortex laser radar, the field angle and the footprint size are larger than those of the traditional laser radar, and a single scanning can cover the whole target to locate and image the whole target.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a block diagram of a direct probe system on-board laser radar system;
FIG. 2 is a block diagram of a coherent probe system satellite-borne lidar receiver;
FIG. 3 is a block diagram of a vortex lidar system;
FIG. 4 is a cross-sectional phase profile of Gaussian-Laguerre lasers of different radial quantum numbers, angular quantum numbers at the same transmission distance;
FIG. 5 shows vortex laser echo phase information of square, triangular and circular targets in sequence;
FIG. 6 is a schematic diagram of a column-by-column continuous search overlay;
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
The vortex laser-based spaceborne wide-field laser radar is mounted on a solar synchronous orbit (polar orbit) satellite. Referring to fig. 3, the invention provides a vortex laser-based satellite-borne wide-field laser radar, which comprises a seed light source, a vortex modulator, a telescope, a vortex demodulator, a detector and a data processing unit. The vortex modulator and the vortex demodulator respectively modulate output laser into vortex laser and de-vortex imaging echo signals.
In a single scanning work flow, common Gaussian laser generated by a seed light source is changed into vortex laser after passing through a vortex modulator, an echo is generated after the vortex laser irradiates a target, the vortex laser is received by a telescope, demodulated by the vortex demodulator, enters a detector for imaging, and finally data processing is carried out.
As shown in fig. 4, by utilizing the characteristic that vortex laser contains regular phase information, the minimum resolvable signal-to-noise ratio can be reduced by at least but not limited to two orders of magnitude, and the satellite-borne laser radar based on vortex laser can effectively perform echo signal detection under the interference of background light radiation such as earth spontaneous radiation, sunlight ground reflection, atmospheric scattering and the like, namely the satellite-borne laser radar based on vortex laser can perform work all day long.
The space-based vortex laser radar provided by the invention can increase the angle of view and the laser footprint range on the basis of ensuring the resolution capability of echo signals due to the reduction of the requirement on the signal-to-noise ratio.
The vortex laser carries regular phase information, and after the vortex laser is modulated (reflected and diffracted) by targets with different shapes, the echo signals carry the information of the shape characteristics of the targets, so that the shape type of the targets can be identified by analyzing the phase information characteristics of the echoes, and the echo phase information is shown in figure 5 by taking the targets with a plurality of special shapes as examples; the invention relates to a satellite-borne laser radar which utilizes the method to identify the shape type of a target;
when capturing targets existing in the potential range of the targets, vortex laser radar is utilized to generate vortex laser, a search strategy of continuous scanning column by column is adopted, full coverage scanning search is performed in the range, as shown in fig. 6, the vortex laser irradiates the targets to reflect and receive echo signals, and accurate imaging and recognition of the targets are achieved by combining the target type recognition capability.
The invention will be described in more detail below by means of a preferred embodiment. This example gives a detailed implementation and a specific procedure based on the localization of an object of about 50m x 50m size for an artefact, but the scope of protection of the invention is not limited to the examples described below.
The prior information or infrared detection means determines that the target exists in a region of 100km multiplied by 100km, and the region is called as a target potential interval;
the seed light source generates common Gaussian laser;
the common Gaussian laser is changed into vortex laser after being modulated by the vortex modulator;
vortex laser is emitted from the telescope to irradiate a target potential zone;
the single scanning is a circular field vortex laser pulse signal with a radius of 2.5 km;
full coverage scanning is performed on the whole target potential interval by adopting but not limited to a search strategy of continuous scanning column by column, and the following equation is adopted:
wherein d r Represents the scanning interval in the column, R represents the inner diameter of the light spot, R represents the outer diameter of the light spot, d c Representing the inter-column scan spacing.
Vortex laser irradiates the target to reflect and the telescope receives echo signals;
the echo is de-vortexed after passing through the vortex demodulator;
imaging the echo signals after vortex shedding on the detector;
and (3) performing imaging information and other information analysis on the data processing unit to complete target capturing and imaging.
The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily without conflict.

Claims (8)

1. A vortex laser-based spaceborne wide field of view lidar, characterized by being onboard a satellite, comprising: the device comprises a seed light source, a vortex modulator, a telescope, a vortex demodulator, a detector and a data processing unit;
the seed light source is used for generating Gaussian laser and transmitting the Gaussian laser to the vortex modulator;
the vortex modulator is used for modulating Gaussian laser into vortex laser;
the telescope is used for transmitting vortex laser and receiving echo light signals generated by the vortex laser reflected by the detection target;
the vortex demodulator is used for de-vortex the echo optical signal;
the detector is used for imaging the echo optical signals after the vortex is released;
the data processing unit is used for carrying out data processing according to imaging.
2. The vortex laser based spaceborne wide field of view lidar of claim 1, wherein the echo signal is resolved under low signal to noise ratio conditions using phase information contained in the vortex laser; wherein the low signal-to-noise condition includes a condition where the earth black body radiates and sunlight ground reflected light as background noise.
3. The vortex laser-based spaceborne wide-field laser radar according to claim 1, wherein vortex laser is adopted as a carrier wave, phase information of echoes after reflection of objects with different shapes shows a specialized morphological characteristic, and the shape type of objects contained in a single scan is determined by analyzing the phase information in the echoes, so that interference of non-target objects with the same type is eliminated.
4. The vortex laser-based spaceborne wide-field laser radar according to claim 1, wherein in a single scanning work flow, common Gaussian laser generated by a seed light source is changed into vortex laser after passing through a vortex modulator, echoes are generated after the vortex laser irradiates a target, the vortex laser is received by a telescope, demodulated by a vortex demodulator, then the vortex laser enters a detector for imaging, and finally data processing is carried out.
5. The vortex laser based spaceborne wide field of view laser radar of claim 1, wherein when capturing a target existing in a target potential range, vortex laser is generated by using the vortex laser radar, and a search strategy of sequential scanning column by column is adopted to search for full coverage scanning in the range.
6. The vortex laser based spaceborne wide field of view laser radar of claim 1, wherein vortex laser irradiates on a target to reflect and receive echo signals, and imaging and identification of the target are achieved in combination with target type identification capability.
7. The vortex laser-based satellite-borne wide-field-of-view laser radar according to claim 1, wherein the vortex laser annular light spot full-coverage scanning strategy is adopted to perform scanning to realize the full coverage of the area, and the following equation is adopted:
wherein d r Represents the scanning interval in the column, R represents the inner diameter of the light spot, R represents the outer diameter of the light spot, d c Representing the inter-column scan spacing.
8. A satellite comprising the vortex laser based spaceborne wide field of view lidar of any of claims 1 to 7.
CN202311296238.9A 2023-10-08 2023-10-08 Vortex laser-based spaceborne wide-field laser radar Pending CN117538849A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311296238.9A CN117538849A (en) 2023-10-08 2023-10-08 Vortex laser-based spaceborne wide-field laser radar

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311296238.9A CN117538849A (en) 2023-10-08 2023-10-08 Vortex laser-based spaceborne wide-field laser radar

Publications (1)

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CN117538849A true CN117538849A (en) 2024-02-09

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Country Status (1)

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