Laser heterodyne atmospheric remote sensing device and method applied to a ship

Abstract

The application relates to the technical field of laser heterodyne atmospheric remote sensing, and discloses a laser heterodyne atmospheric remote sensing device and method applied to a ship, the device comprising a sun tracking module, a heterodyne light path module, a signal processing module and a computer device, wherein the sun tracking module comprises a sun tracking meter, a photoelectric detector and an optical switch, the heterodyne light path module comprises a laser, an optical attenuator, an optical fiber 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. The laser heterodyne atmospheric remote sensing device applied to the ship can reduce the precision requirement of a sun tracking meter for laser heterodyne detection, and realizes spectral detection under the condition that the probability of the alignment precision being within the range of 0.1 degrees is greater than 50%.

Description

Technical Field

[0001] The present 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 a ship-borne moving platform, the continuous rolling of the ship caused by waves causes the sun to change 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 laser heterodyne atmospheric remote sensing detection technology on a ship-borne platform, and propose a laser heterodyne atmospheric remote sensing device for shipboard use. 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 sunlight intensity changes and remove bad pixels based on the second light beam;

[0005] 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 light beam, and the photodetector is used to mix the combined light beam;

[0006] The signal generated after the mixing is passed through the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence, and undergoes radio frequency amplification, bandpass filtering, power detection and correlation demodulation 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 spectrum signal.

[0008] In one embodiment, the signal processing module further includes a signal generator, wherein 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 for a lock-in amplifier.

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

[0010] In one embodiment, 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 radio frequency amplifier, the outlet end of the radio frequency amplifier is connected to the inlet end of the radio frequency filter, the outlet end of the radio frequency 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 shipborne laser heterodyne atmospheric remote sensing method is provided, characterized in that the method is applied to the laser heterodyne atmospheric remote sensing device described above and includes:

[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 and is greater than a threshold value, 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 present invention proposes a laser heterodyne atmospheric remote sensing device for shipboard use, which 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, and 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; the sun tracker is used to collect sunlight, and the 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 the optical switch, and the second light beam is connected to the photodetector, and the photodetector is used to perform Monitoring changes in sunlight intensity and removing bad pixels; 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 fiber combiner is used to combine the attenuated laser beam with the first beam; and the photodetector is used to mix the combined beams; the signal generated after mixing is passed through the sequentially connected radio frequency amplifier, radio frequency filter, power detector, and phase-locked amplifier for radio frequency amplification, bandpass filtering, power detection, and correlation demodulation 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. The shipborne laser heterodyne atmospheric remote sensing device proposed by the present invention can reduce the accuracy requirements of laser heterodyne detection on the sun tracker, achieving spectral detection with a probability greater than 50% when the alignment accuracy is within 0.1 degrees. 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0017] in:

[0018] Figure 1 1 is a schematic structural diagram of a shipborne laser heterodyne atmospheric remote sensing device according to an embodiment;

[0019] Figure 2 A schematic diagram of a local oscillator light step-by-step scanning process for a shipborne laser heterodyne atmospheric remote sensing device according to 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 Schematic diagram of spectral signals obtained by step-wise scanning of local oscillator light in one embodiment. DETAILED DESCRIPTION

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

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

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] See also Figure 1 As shown, Figure 1 A schematic structural diagram of a shipborne laser heterodyne atmospheric remote sensing device provided by one embodiment of the present invention includes: a sun tracking module, a heterodyne optical path module, a signal processing module, and a computer device. 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 lock-in amplifier, and a data acquisition device.

[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 sunlight intensity changes and remove bad pixels based on the second light beam;

[0027] 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 light beam, and the photodetector is used to mix the combined light beam;

[0028] The signal generated after the mixing is passed through the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence, and undergoes radio frequency amplification, bandpass filtering, power detection and correlation demodulation 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 spectrum signal.

[0030] Wherein, the sun tracker is connected to the inlet end of the fiber optic splitter, one outlet end of the fiber optic splitter is connected to one end of the optical switch, the other outlet end of the fiber optic 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 radio frequency amplifier, the outlet end of the radio frequency amplifier is connected to the inlet end of the radio frequency filter, the outlet end of the radio frequency 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 tracks the sun's position in real time, collecting sunlight containing information about atmospheric molecular absorption. This sunlight is then coupled into a single-mode optical fiber via a fiber collimator. A 99:1 fiber beam splitter splits the sunlight into two beams: the 99% beam, the first beam, which is intensity-modulated via an optical switch to improve the signal-to-noise ratio of the heterodyne signal. The second beam, the second beam, is connected to a photodetector to monitor changes in sunlight intensity and remove bad pixels. A computer controls a local oscillator laser for step-wise scanning. After being attenuated by an optical attenuator, the emitted laser beam is combined with sunlight via a 1:1 fiber combiner and mixed on the photosensitizing surface of a GHz-bandwidth photodetector. An RF amplifier, RF filter, and power detector amplify, bandpass filter, and detect the power of the resulting DC and difference frequency signals. A lock-in amplifier performs correlation demodulation on the conditioned heterodyne signal. A data acquisition device collects and transmits the demodulated signal to a computer.

[0032] In one embodiment, referring to Figure 2 , Figure 2 This is a schematic diagram of the LO light step-scanning process. The computer sends commands to the laser driver at regular intervals, changing the control parameters in equal steps to perform a step-by-step scan. The LO light wavelength can be tuned in steps by maintaining a fixed temperature and then changing the current, or by maintaining a fixed current and then changing the temperature. The tuning range encompasses the target absorption spectrum. The duration of a single step is preferably 0.1 to 10 seconds, increasing with increasing tilt. The total number of steps is preferably 50 to 100, ensuring that the wavelength covers the entire absorption spectrum.

[0033] In one embodiment, the signal processing module further includes a signal generator, wherein 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 for a lock-in amplifier.

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

[0035] In one embodiment, referring to 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. Signals below the threshold are discarded, and the retained signals are averaged as the spectrum measurement result of the step. The data of all steps are processed cyclically, and the spectrum measurement results obtained are combined into a complete spectrum signal. The schematic diagram of the spectrum signal obtained by the local oscillator step scanning is shown in Figure 4 As shown in the figure, the spectral signal obtained by the LO step-scan method is the result of normalizing the complete spectral signal. By combining the spectral signal obtained by the LO step-scan method with the prior profiles of temperature, pressure, and concentration, and using optimal estimation or other algorithms, the entire atmospheric column concentration and profile information of the target greenhouse gas can be calculated.

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

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

[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 and is greater than a threshold value, 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 will clearly understand that for the sake of convenience and brevity 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 they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A shipborne laser heterodyne atmospheric remote sensing device, characterized in that: 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, and 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 acquisition device; 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 sunlight intensity changes and remove bad pixels based on the second light beam; 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 light beam, and the photodetector is used to mix the combined light beam; The signal generated after the mixing is passed through the radio frequency amplifier, the radio frequency filter, the power detector and the phase-locked amplifier connected in sequence, and undergoes radio frequency amplification, bandpass filtering, power detection and correlation demodulation 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 spectrum signal.

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

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

4. The shipborne laser heterodyne atmospheric remote sensing device 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 radio frequency amplifier, the outlet end of the radio frequency amplifier is connected to the inlet end of the radio frequency filter, the outlet end of the radio frequency 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 and is greater than a threshold value, 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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