Shipborne laser heterodyne atmosphere remote sensing device and method

Abstract

The invention relates to the technical field of laser heterodyne atmosphere remote sensing, and discloses a shipborne laser heterodyne atmosphere remote sensing device and method.The device comprises a sun tracking module, a heterodyne light path module, a signal processing module and computer equipment, the sun tracking module comprises a sun tracker, a photoelectric detector and an optical switch, and the heterodyne light path module is connected with the computer equipment; the heterodyne optical path module comprises a laser, an optical attenuator, an optical fiber beam combiner and a photoelectric detector; the signal processing module comprises a radio frequency amplifier, a radio frequency filter, a power detector, a lock-in amplifier and a data collector. Through the shipborne laser heterodyne atmosphere remote sensing device provided by the invention, the precision requirement of laser heterodyne detection on a sun tracker can be reduced, and spectrum detection under the condition that the probability is greater than 50% when the alignment precision is within a 0.1-degree range is realized.

Description

Technical Field

[0001] The invention relates to the technical field of laser heterodyne atmospheric remote sensing, and in particular to a shipborne laser heterodyne atmospheric remote sensing device and method. Background Art

[0002] On the ship-borne moving platform, due to the continuous tilting of the hull caused by waves, the sun changes rapidly at the Hz level relative to the sun tracker. Ordinary sun trackers cannot continuously track the sun and continuously obtain sunlight signals, so laser heterodyne atmospheric remote sensing detection on the ship-borne platform cannot be realized. Summary of the invention

[0003] Based on this, it is necessary to address the problem that the existing technology cannot realize the laser heterodyne atmospheric remote sensing detection technology on the ship-borne platform, and propose a laser heterodyne atmospheric remote sensing device for shipboard, the laser heterodyne atmospheric remote sensing device includes: a sun tracking module, a heterodyne optical path module, a signal processing module and a computer device, wherein the sun tracking module includes a sun tracker, a photodetector and an optical switch, the heterodyne optical path module includes a laser, an optical attenuator, a fiber combiner, and a photodetector; the signal processing module includes a radio frequency amplifier, a radio frequency filter, a power detector, a phase-locked amplifier and a data collector;

[0004] The sun tracker is used to collect sunlight, and the optical fiber beam splitter is used to split the sunlight into a first light beam and a second light beam, wherein the first light beam is intensity modulated by an optical switch, and the second light beam is connected to the photodetector, and the photodetector is used to monitor the change of sunlight intensity and remove bad pixels based on the second light beam;

[0005] The computer device is used to control the laser to perform step-wise scanning to generate a radiated laser beam, the optical attenuator is used to attenuate the radiated laser beam, the optical fiber combiner is used to combine the attenuated laser beam with the first light beam, and the photodetector is used to mix the combined light beam;

[0006] The signal generated after mixing is subjected to radio frequency amplification, bandpass filtering, power detection and correlation demodulation by the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence to obtain a heterodyne detection signal. The data collector is used to collect the heterodyne detection signal and transmit it to the computer device.

[0007] The computer device is used to process the heterodyne detection signal to obtain a spectral signal.

[0008] In one embodiment, the signal processing module further includes a signal generator, and the signal generator is used to generate a square wave signal, and the square wave signal is used to control the optical switch and serve as a reference signal of a lock-in amplifier.

[0009] In one embodiment, the sun tracker is connected to the inlet end of the fiber optic beam splitter, one outlet end of the fiber optic beam splitter is connected to one end of the optical switch, the other outlet end of the fiber optic beam splitter is connected to the photodetector, one inlet end of the fiber optic combiner is connected to the other end of the optical switch, and the other inlet end of the fiber optic combiner is connected to the outlet end of the optical attenuator.

[0010] In one embodiment, the outlet end of the fiber optic combiner is connected to the inlet end of the photodetector, the outlet end of the photodetector is connected to the inlet end of the RF amplifier, the outlet end of the RF amplifier is connected to the inlet end of the RF filter, the outlet end of the RF filter is connected to the inlet end of the power detector, the outlet end of the power detector is connected to the inlet end of the phase-locked amplifier, the outlet end of the phase-locked amplifier is connected to the inlet end of the data collector, the outlet end of the data collector is connected to the computer device, and the computer device is connected to the laser.

[0011] In one embodiment, a ship-borne laser heterodyne atmospheric remote sensing method is provided, characterized in that the method is applied to the laser heterodyne atmospheric remote sensing device as described above, and comprises:

[0012] In response to the laser heterodyne atmospheric remote sensing instruction, controlling the laser heterodyne atmospheric remote sensing device to collect heterodyne detection signals;

[0013] For heterodyne detection signals collected in each wavelength step of step-by-step scanning in a laser heterodyne atmospheric remote sensing device, the sunlight intensity corresponding to the heterodyne detection signals collected in the wavelength step is averaged to obtain a spectrum measurement result corresponding to the wavelength step;

[0014] The spectral measurement results corresponding to each wavelength step are combined into a complete spectral signal, and based on the complete spectral signal, the entire atmospheric column concentration and profile information of the target greenhouse gas are calculated.

[0015] The laser heterodyne atmospheric remote sensing device for shipboard proposed by the present invention comprises: a sun tracking module, a heterodyne optical path module, a signal processing module and a computer device, wherein the sun tracking module comprises a sun tracker, a photodetector and an optical switch, and the heterodyne optical path module comprises a laser, an optical attenuator, an optical fiber combiner and a photodetector; the signal processing module comprises a radio frequency amplifier, a radio frequency filter, a power detector, a phase-locked amplifier and a data collector; the sun tracker is used to collect sunlight, and the optical fiber beam splitter is used to divide the sunlight into a first light beam and a second light beam, wherein the first light beam is intensity modulated by the optical switch, and the second light beam is connected to the photodetector, and the photodetector is used to perform Sunlight intensity change monitoring and bad pixel removal; the computer device is used to control the laser to perform step-by-step scanning to generate a radiated laser beam, the optical attenuator is used to attenuate the radiated laser beam, the optical fiber combiner is used to combine the attenuated laser beam with the first beam, and the photoelectric detector is used to mix the combined beam; the signal generated after mixing is passed through the RF amplifier, RF filter, power detector and phase-locked amplifier connected in sequence, and RF amplification, bandpass filtering, power detection and correlation demodulation are performed to obtain a heterodyne detection signal, the data acquisition device is used to collect the heterodyne detection signal and transmit it to the computer device; the computer device is used to process the heterodyne detection signal to obtain a spectral signal. Through the laser heterodyne atmospheric remote sensing device for shipboard proposed by the present invention, the accuracy requirements of laser heterodyne detection on the sun tracker can be reduced, and spectral detection can be achieved when the probability of alignment accuracy within 0.1 degree is greater than 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] in:

[0018] Figure 1 Schematic diagram of the structure of a laser heterodyne atmospheric remote sensing device used on board a ship in one embodiment;

[0019] Figure 2 A schematic diagram of a local oscillator light step-type scanning process of a ship-borne laser heterodyne atmospheric remote sensing device in one embodiment;

[0020] Figure 3A schematic diagram of a spectral signal obtained within a single wavelength step of a laser heterodyne atmospheric remote sensing device in one embodiment;

[0021] Figure 4 It is a schematic diagram of a spectrum signal obtained by step-by-step scanning of the local oscillator light in one embodiment. DETAILED DESCRIPTION

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0023] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1 As shown, Figure 1 A schematic diagram of the structure of a ship-borne laser heterodyne atmospheric remote sensing device provided by an embodiment of the present invention, wherein the ship-borne laser heterodyne atmospheric remote sensing device comprises: a sun tracking module, a heterodyne optical path module, a signal processing module and a computer device, wherein the sun tracking module comprises a sun tracker, a photodetector and an optical switch, and the heterodyne optical path module comprises a laser, an optical attenuator, a fiber combiner and a photodetector; the signal processing module comprises a radio frequency amplifier, a radio frequency filter, a power detector, a phase-locked amplifier and a data collector;

[0026] The sun tracker is used to collect sunlight, and the optical fiber beam splitter is used to split the sunlight into a first light beam and a second light beam, wherein the first light beam is intensity modulated by an optical switch, and the second light beam is connected to the photodetector, and the photodetector is used to monitor the change of sunlight intensity and remove bad pixels based on the second light beam;

[0027] The computer device is used to control the laser to perform step-wise scanning to generate a radiated laser beam, the optical attenuator is used to attenuate the radiated laser beam, the optical fiber combiner is used to combine the attenuated laser beam with the first light beam, and the photodetector is used to mix the combined light beam;

[0028] The signal generated after mixing is subjected to radio frequency amplification, bandpass filtering, power detection and correlation demodulation by the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence to obtain a heterodyne detection signal. The data collector is used to collect the heterodyne detection signal and transmit it to the computer device.

[0029] The computer device is used to process the heterodyne detection signal to obtain a spectral signal.

[0030] Wherein, the sun tracker is connected to the inlet end of the fiber optic beam splitter, one outlet end of the fiber optic beam splitter is connected to one end of the optical switch, the other outlet end of the fiber optic beam splitter is connected to the photodetector, one inlet end of the fiber optic combiner is connected to the other end of the optical switch, the other inlet end of the fiber optic combiner is connected to the outlet end of the optical attenuator, the outlet end of the fiber optic combiner is connected to the inlet end of the photodetector, the outlet end of the photodetector is connected to the inlet end of the RF amplifier, the outlet end of the RF amplifier is connected to the inlet end of the RF filter, the outlet end of the RF filter is connected to the inlet end of the power detector, the outlet end of the power detector is connected to the inlet end of the phase-locked amplifier, the outlet end of the phase-locked amplifier is connected to the inlet end of the data collector, the outlet end of the data collector is connected to the computer device, and the computer device is connected to the laser.

[0031] As an example, a sun tracker is used to track the position of the sun in real time, collect sunlight containing information on the absorption of atmospheric molecules, and couple the sunlight into a single-mode optical fiber through a fiber collimator. A 99:1 fiber beam splitter divides the sunlight into two beams, of which the 99% beam is the first beam, which is intensity modulated by an optical switch to improve the signal-to-noise ratio of the heterodyne signal, and the other beam is the second beam, which is connected to a photodetector to monitor the intensity change of sunlight for bad pixel removal. The computer controls the local oscillator laser to perform step-by-step scanning. After the radiated laser beam is attenuated by the optical attenuator, it is combined with sunlight through a 1:1 fiber beam combiner and mixed on the photosensitive surface of a GHz-level bandwidth photodetector. The RF amplifier, RF filter and power detector perform RF amplification, bandpass filtering and power detection on the DC signal and difference frequency signal generated after mixing. The phase-locked amplifier performs correlation demodulation on the conditioned heterodyne signal, and the data acquisition device collects the demodulated signal and transmits it to the computer device.

[0032] In one embodiment, reference Figure 2 , Figure 2 This is a schematic diagram of the step-by-step scanning process of the local oscillator. The computer device sends instructions to the laser driver at regular intervals, changes the control parameters with the same step size, and performs step-by-step scanning. The wavelength of the local oscillator can be tuned step by step by fixing the temperature and changing the current or fixing the current and changing the temperature. The tuning range includes the target absorption spectrum. The time of a single step is preferably 0.1 to 10 seconds. The time of a single step increases with the increase in the degree of tilting. The overall number of steps is preferably 50 to 100, and the wavelength can cover the entire absorption spectrum.

[0033] In one embodiment, the signal processing module further includes a signal generator, and the signal generator is used to generate a square wave signal, and the square wave signal is used to control the optical switch and serve as a reference signal of a lock-in amplifier.

[0034] In one embodiment, sunlight containing absorption information of atmospheric molecules is collected by the above-mentioned sun tracker and coupled into a single-mode optical fiber. Intensity modulation is performed through an optical switch. The laser beam radiated by the local oscillator laser in a step-by-step scanning manner is attenuated by an optical attenuator and then combined with the sunlight through a 1:1 optical fiber combiner. The laser beam is mixed on the photosensitive surface of a photodetector with a bandwidth of the order of GHz. The detector converts the optical signal into an electrical signal, which is demodulated by a phase-locked amplifier after radio frequency amplification, bandpass filtering and power detection to obtain a heterodyne detection signal.

[0035] In one embodiment, reference Figure 3 , the schematic diagram of the spectral signal obtained within a single wavelength step is as follows Figure 3, the heterodyne detection signal is segmented according to the step time, and each data in the wavelength step is read cyclically to determine whether the sunlight intensity at that point is greater than the threshold, and the signal less than the threshold is discarded. The retained signal is averaged as the spectrum measurement result of the step, and the data of all steps are processed cyclically to form a complete spectrum signal with the obtained spectrum measurement results. The schematic diagram of the spectrum signal obtained by the local oscillation light step scanning is shown in Figure 4 As shown in the figure, the spectral signal obtained by the local oscillator step scanning is the result of normalizing the complete spectral signal. The spectral signal obtained by the local oscillator step scanning is combined with the prior profiles of temperature, pressure and concentration, and the optimal estimate or other algorithms are used to calculate the concentration and profile information of the entire atmospheric column of the target greenhouse gas.

[0036] The shipborne laser heterodyne atmospheric remote sensing device proposed by the present invention reduces the accuracy requirement of laser heterodyne detection on the sun tracker, and realizes spectrum detection when the probability of alignment accuracy within 0.1 degree is greater than 50%.

[0037] In one embodiment, a shipborne laser heterodyne atmospheric remote sensing method is applied to the shipborne laser heterodyne atmospheric remote sensing device as described above, and the method includes:

[0038] In response to the laser heterodyne atmospheric remote sensing instruction, controlling the laser heterodyne atmospheric remote sensing device to collect heterodyne detection signals;

[0039] For heterodyne detection signals collected in each wavelength step of step-by-step scanning in a laser heterodyne atmospheric remote sensing device, the sunlight intensity corresponding to the heterodyne detection signals collected in the wavelength step is averaged to obtain a spectrum measurement result corresponding to the wavelength step;

[0040] The spectral measurement results corresponding to each wavelength step are combined into a complete spectral signal, and based on the complete spectral signal, the entire atmospheric column concentration and profile information of the target greenhouse gas are calculated.

[0041] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0042] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A shipborne laser heterodyne atmospheric remote sensing device, characterized in that: The laser heterodyne atmospheric remote sensing device comprises: a sun tracking module, a heterodyne optical path module, a signal processing module and a computer device, wherein the sun tracking module comprises a sun tracker, a photoelectric detector and an optical switch, and the heterodyne optical path module comprises a laser, an optical attenuator, a fiber combiner and a photoelectric detector; the signal processing module comprises a radio frequency amplifier, a radio frequency filter, a power detector, a phase-locked amplifier and a data collector; The sun tracker is used to collect sunlight, and the optical fiber beam splitter is used to split the sunlight into a first light beam and a second light beam, wherein the first light beam is intensity modulated by an optical switch, and the second light beam is connected to the photodetector, and the photodetector is used to monitor the change of sunlight intensity and remove bad pixels based on the second light beam; The computer device is used to control the laser to perform step-wise scanning to generate a radiated laser beam, the optical attenuator is used to attenuate the radiated laser beam, the optical fiber combiner is used to combine the attenuated laser beam with the first light beam, and the photodetector is used to mix the combined light beam; The signal generated after mixing is subjected to radio frequency amplification, bandpass filtering, power detection and correlation demodulation by the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence to obtain a heterodyne detection signal. The data collector is used to collect the heterodyne detection signal and transmit it to the computer device. The computer device is used to process the heterodyne detection signal to obtain a spectral signal.

2. The laser heterodyne atmospheric remote sensing device for shipboard use according to claim 1, characterized in that: The signal processing module further includes a signal generator, and the signal generator is used to generate a square wave signal, and the square wave signal is used to control the optical switch and serve as a reference signal of a lock-in amplifier.

3. The laser heterodyne atmospheric remote sensing device for shipboard use according to claim 1, characterized in that: The sun tracker is connected to the inlet end of the fiber optic beam splitter, one outlet end of the fiber optic beam splitter is connected to one end of the optical switch, the other outlet end of the fiber optic beam splitter is connected to the photodetector, one inlet end of the fiber optic combiner is connected to the other end of the optical switch, and the other inlet end of the fiber optic combiner is connected to the outlet end of the optical attenuator.

4. The laser heterodyne atmospheric remote sensing device for shipboard use according to claim 1, characterized in that: The outlet end of the optical fiber combiner is connected to the inlet end of the photodetector, the outlet end of the photodetector is connected to the inlet end of the RF amplifier, the outlet end of the RF amplifier is connected to the inlet end of the RF filter, the outlet end of the RF filter is connected to the inlet end of the power detector, the outlet end of the power detector is connected to the inlet end of the phase-locked amplifier, the outlet end of the phase-locked amplifier is connected to the inlet end of the data collector, the outlet end of the data collector is connected to the computer device, and the computer device is connected to the laser.

5. A shipborne laser heterodyne atmospheric remote sensing method, characterized in that: The method applied to the shipborne laser heterodyne atmospheric remote sensing device according to any one of claims 1 to 4 comprises: In response to the laser heterodyne atmospheric remote sensing instruction, controlling the laser heterodyne atmospheric remote sensing device to collect heterodyne detection signals; For heterodyne detection signals collected in each wavelength step of step-by-step scanning in a laser heterodyne atmospheric remote sensing device, the sunlight intensity corresponding to the heterodyne detection signals collected in the wavelength step is averaged to obtain a spectrum measurement result corresponding to the wavelength step; The spectral measurement results corresponding to each wavelength step are combined into a complete spectral signal, and based on the complete spectral signal, the entire atmospheric column concentration and profile information of the target greenhouse gas are calculated.

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