CN101071171A - Dualwavelength dual-field Mie scattering laser radar structure and its detecting method - Google Patents

Abstract

The invention discloses a structure and detection method of a dual-wavelength dual-field-of-view meter-scattering laser radar, which includes a laser emitting unit echo signal receiving unit, a subsequent optical unit, a signal detection and acquisition unit, and a control unit; the laser emitting The unit adopts Nd:YAG laser, and emits laser pulses with two wavelengths of 532nm and 1064nm at the same time, which are received by two receiving telescopes with diameters of 400mm and 200mm respectively. After the two receiving telescopes are subsequent optical units, and the optical signals from the subsequent optical units Received by the signal detection and acquisition unit and the control unit. The dual receiving channels are used for the simultaneous detection of 532nm and 1064nm in the upper and lower layers respectively. Each channel has its own independent field of view, which can take into account the requirements of the low detection blind area with a large field of view at the low layer and the detection height with a small field of view at the high layer; respectively detect 532nm and 1064nm The vertical profile and continuous distribution of the extinction coefficient of the atmospheric aerosol, as well as the continuous distribution of the horizontal extinction coefficient, can obtain various optical parameters of the atmospheric aerosol through analysis.

Description

Structure and detection method of dual-wavelength dual-field-of-view meter scattering lidar

technical field

The invention relates to the field of radar detection, in particular to a structure of a dual-wavelength dual-field-of-view meter scattering laser radar and a detection method thereof.

Background technique

Lidar uses laser light as a light source to remotely sense the atmosphere by detecting the radiation signal of the interaction between the laser and the atmosphere. The interaction between the laser and the atmosphere generates radiation signals containing information about gas molecules and aerosol particles, from which information about gas molecules and aerosol particles can be obtained by using the inversion method.

Lidar is the product of the combination of traditional radar technology and modern laser technology. In the second year after the advent of the laser, that is, in 1961, scientists proposed the idea of laser radar and carried out research work. For more than 40 years, with the rapid development of laser technology and the application of advanced signal detection and data acquisition systems, LiDAR has become an important active remote sensing tool due to its high measurement accuracy, fine temporal and spatial resolution, and large detection span.

At present, the meter-scattering lidar system for detecting tropospheric aerosols generally has the following three deficiencies: first, the system is relatively complex, bulky, heavy, and difficult to move and transport, which limits its application area; secondly, the detection The height is limited, most of them are limited to the boundary layer below 5-6km, the detection height is lower during the day, and the reliability of the third long-term continuous operation is often poor.

In order to overcome the above-mentioned shortcomings and deficiencies of the conventional meter scattering lidar, a kind of Micro Pulse Lidar (MPL for short) has come out internationally. However, because its output energy is on the order of μJ, it relies on a high repetition rate (thousands of Hz) to improve the detection signal-to-noise ratio, so the detection time is long, and the detection height during the day is only 6km, and if its geometric overlap factor is too long (about 4km) If it cannot be determined accurately, it will bring large errors to the aerosol detection results.

Contents of the invention

The object of the present invention is to provide a structure and detection method of a dual-wavelength dual-field-of-view meter scattering lidar with strong reliability and high accuracy.

The present invention can be realized through the following technical solutions:

A structure of dual-wavelength dual-field-of-view meter scattering lidar, characterized in that it includes a laser emitting unit, an echo signal receiving unit, a subsequent optical unit, a signal detection and acquisition unit, and a control unit; the laser emitting unit includes Nd : YAG laser, the laser emits laser pulses with two wavelengths of 532nm and 1064nm, an echo signal receiving unit is arranged on the optical axis parallel to the output optical axis of the laser, and the echo signal receiving unit includes a receiving telescope with a diameter of 200mm and Receiving telescope with a diameter of 400mm, the subsequent optical path of the receiving telescope with a diameter of 400mm is arranged in sequence with a small hole diaphragm, a mirror, an eyepiece and a beam splitter; the optical path after the beam splitter is divided into two paths, one path is connected to the photon counting through a 1064nm narrow-band filter Detector, the output circuit of the photon counting detector is provided with an amplifier VT120, and the output circuit of the amplifier VT120 is provided with a photon counting card MCS, and the photon counting card MCS sends the collected signal to the computer for processing; The light sheet is connected to the analog detector, and an amplifier 777 is arranged on the subsequent optical path of the analog detector, and an A/D data acquisition card is arranged on the output circuit of the amplifier 777, and the A/D data acquisition card sends the collected digital signal to the computer for processing. Processing; the subsequent optical path of the receiving telescope with a diameter of 200mm is arranged in sequence with a small hole diaphragm and an eyepiece; the eyepiece transmits the signal to the beam splitter through an optical fiber, and the optical path after the beam splitter is divided into two paths, one of which is connected to the photons through a 1064nm narrow-band filter Counting detector, the output circuit of the photon counting detector is provided with an amplifier VT120, and the output circuit of the amplifier VT120 is provided with a photon counting card MCS, which sends the collected signal to the computer for processing; the other channel passes through a 532nm narrowband The optical filter is connected to the analog detector, the output circuit of the analog detector is provided with an amplifier 777, and the output circuit of the amplifier 777 is provided with an A/D data acquisition card, and the A/D data acquisition card sends the collected digital signal to the computer to process.

The detection method of dual-wavelength dual-field-of-view meter scattering laser radar is characterized in that it includes a laser emitting unit echo signal receiving unit, a subsequent optical unit, a signal detection and acquisition unit and a control unit; the laser emitting unit adopts Nd:YAG The laser emits laser pulses with two wavelengths of 532nm and 1064nm at the same time, which are received by two receiving telescopes with diameters of 400mm and 200mm respectively; the light received by the receiving telescope with a diameter of 400mm passes through the aperture diaphragm, is reflected by the reflector to the eyepiece, and is emitted in parallel , after passing through the beam splitter, it is divided into two beams of light, one is reflected light with a wavelength of 1064nm, and the other is transmitted light with a wavelength of 532nm; 98% of the reflected light with a wavelength of 1064nm is filtered by a 1064nm narrow-band filter and then converted into an electric current by a photon counting detector. After the signal is amplified by the amplifier VT120, it is collected by the photon counting card MCS and sent to the computer for data storage, processing and real-time display; 85% of the transmitted light with a wavelength of 532nm is filtered by a 532nm narrow-band filter, and then photoelectrically converted by the analog detector. After the 777 is amplified, it is collected by the A/D data acquisition card and sent to the computer for data storage, processing and real-time display; the light received by the receiving telescope with a diameter of 200mm passes through the aperture diaphragm, and then is converged and coupled through the eyepiece to the optical fiber, and then passes through the beam splitter Divided into two beams of light, one beam is 1064nm wavelength reflected light, the other is 532nm wavelength transmitted light, 98% of 1064nm wavelength reflected light is filtered by 1064nm narrow-band filter, converted into electrical signal by photon counting detector, and amplified by amplifier VT120 Afterwards, it is collected by the photon counting card MCS and sent to the computer for data storage, processing and real-time display; 85% of the transmitted light with a wavelength of 532nm is filtered by a 532nm narrow-band filter, and then photoelectrically converted by an analog detector. D The data acquisition card collects and sends it to the computer for data storage, processing and real-time display; the computer controls the laser to emit light through the RS232 serial port, and the Q-Switch synchronous signal output by the laser passes through the main wave generator to generate the main wave signal. to two photon counting cards MCS and two A/D data acquisition cards as the trigger signals of the four acquisition boards, and the other two channels are respectively sent to the photon counting detector and the analog detector behind the receiving telescope with a diameter of 400mm as two The gating signal of a detector.

The receiving telescope with a diameter of 400mm adopts a small field of view, and the size of the field of view is adjusted by an aperture diaphragm to receive backscattered echo signals from the upper atmosphere.

The receiving telescope with a diameter of 200mm adopts a large receiving field of view.

The following are the main technical parameters of the dual-wavelength dual-field-of-view meter scattering lidar system of the present invention:

parameter name Parameter value Laser emission unit Laser wavelength/nm single pulse energy/mJ pulse repetition frequency/Hz beam divergence angle/mrad beam linear polarization degree/% Nd:YAG532/1064120/90201.599 Receiving optical unit telescope aperture/mm field of view/mrad filter central wavelength/nm Cassegrain400/2001/4532/1064

  Filter bandwidth/nm 0.25/0.5   Signal detection and acquisition unit Photomultiplier tube pre-signal amplifier A/D data acquisition card Photon counting card Sampling time interval/ns R7400U/H7680/R3636VT120/777Gage 1610MCS200

The present invention has the following characteristics:

1. The dual receiving channels are used for simultaneous detection of 532nm and 1064nm in the upper and lower layers respectively. Each channel has its own independent field of view, which can take into account the requirements of low detection blind area with large field of view in the low layer and detection height with small field of view in the high layer;

2. Simultaneous detection of high and low layers effectively shortens the time for obtaining atmospheric information;

3. The low-level receiving channel can perform horizontal detection, which can correct the overlap factor and detect the horizontal visibility of the atmosphere;

4. Detect the vertical profile and continuous distribution of 532nm and 1064nm atmospheric aerosol extinction coefficients, and the continuous distribution of horizontal extinction coefficients respectively, and various optical parameters of atmospheric aerosols can be obtained through analysis.

Description of drawings

Fig. 1 is a block diagram of the present invention;

Fig. 2 is another optical path diagram of the subsequent optical system unit of the receiving telescope with a diameter of 400mm;

Fig. 3 is another optical path diagram of the subsequent optical system unit of the receiving telescope with a diameter of 200 mm;

Fig. 4 is a working flow diagram of the dual-wavelength dual-field-of-view meter scattering lidar system;

Figure 5 is a diagram of the actual echo signal at 532nm wavelength detected by the dual-wavelength dual-field-of-view meter scattering lidar;

Figure 6 is a diagram of the actual echo signal at 1064nm wavelength detected by the dual-wavelength dual-field-of-view meter scattering lidar;

Figure 7 is a comparison diagram of the 532nm actual atmospheric backscatter echo signal detected by the dual-wavelength dual-field-of-view meter scattering lidar and the numerical simulation calculation signal;

Figure 8 is a test result diagram of the linearity of the atmospheric backscatter echo signal of the dual-wavelength dual-field-of-view m-scattering lidar;

Fig. 9 is a vertical profile diagram of the atmospheric aerosol extinction coefficient of 532nm and 1064mm wavelengths detected by the dual-wavelength dual-field-of-view meter scattering lidar;

Figure 10 is a comparison chart of the vertical profile of the atmospheric aerosol extinction coefficient detected by the dual-wavelength dual-field-of-view meter-scattering lidar (DWL) and the polarized meter-scattering lidar (PML);

Figure 11 is a graph showing the changes in atmospheric digestion coefficient detected for 25 consecutive hours from 17:00 on January 9 to 18:00 on January 10, 2007;

Figure 12 is a comparison chart of the change in atmospheric horizontal visibility detected by the dual-wavelength dual-field-of-view meter-scattering lidar and Vaisala from 17:00 on January 9, 2007 to 18:00 on the 10th for 25 consecutive hours;

Figure 13 is a comparison result of the optical depth of the atmosphere detected by the dual-wavelength dual-field-of-view meter scattering lidar and the radiometer from 10:00 to 14:00 on January 8;

Detailed ways

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is a structural block diagram of the present invention, which includes a laser emitting unit, an echo signal receiving unit, a subsequent optical unit, a signal detection and acquisition unit, and a control unit. The laser emitting unit includes a Nd:YAG laser, and the echo signal receiving unit includes a receiving telescope with a diameter of 200mm and a receiving telescope with a diameter of 400mm.

Fig. 2 is the following optical system unit light path figure of diameter 400mm receiving telescope in the present invention, diameter 400mm receiving telescope adopts small field of view (the size of field of view is regulated by aperture diaphragm) in the figure, receives upper atmosphere backscatter echo signal, can Suppress the strong sky background noise during the day and increase the detection height of the dual-wavelength dual-field-of-view meter scattering lidar. After the light received by the receiving telescope passes through the small hole diaphragm, it is reflected by the mirror to the eyepiece and exits in parallel. After passing through the beam splitter, 98% of the reflected light with a wavelength of 1064nm passes through a 1064nm narrow-band filter and is converted by the photon counting detector to The electrical signal is amplified by the amplifier and collected by the photon counting card; 85% of the 532nm wavelength transmitted light passes through the 532nm narrow-band filter, is converted photoelectrically by the analog detector, and is amplified by the amplifier and collected by the A/D data acquisition card.

Fig. 3 is the optical path diagram of the subsequent optical unit of the receiving telescope with a diameter of 200mm in the present invention. In the figure, the receiving telescope with a diameter of 200mm adopts a large receiving field of view and receives backscattered echo signals from the lower atmosphere, which can reduce the blind area of detection and improve double-wavelength double-vision Accuracy of Field Meter Scattering Lidar for Detection of Extinction Coefficients of Near-Surface Atmospheric Aerosols. After the light received by the receiving telescope passes through the aperture diaphragm, it is converged and coupled to the optical fiber through the eyepiece, and then after passing through the spherical reflector and two reflectors, it is divided into two beams by the beam splitter, which is the same as the high-level, 98% of the 1064nm wavelength The reflected light and 85% of the transmitted light with a wavelength of 532nm pass through the corresponding narrow-band filter, detector and acquisition card respectively to collect the data.

Fig. 4 is the working flow diagram of the dual-wavelength dual-field-of-view meter-scattering lidar system of the present invention, the computer control unit in this system can realize the control to the whole system, realize the collection, transmission and storage of data, and real-time calculation and display measurement data. When detecting the vertical extinction coefficient profile of atmospheric aerosols, first place the two receiving telescopes vertically. After opening the dual-wavelength dual-field-of-view meter scattering lidar system software, perform system self-inspection, and initialize the photon counting card, A/D data acquisition card and laser. After the correct initialization is completed, set the detection parameters as required, including The number of groups to be measured and the number of laser pulses collected for each group are set. After the settings are completed, the laser and the data acquisition card are sent to start working instructions. After the laser emits light, it starts to collect. The collected data is stored, processed and displayed in real time.

Figures 5 and 6 are the actual echo signals at 532nm and 1064nm wavelengths detected by the dual-wavelength dual-field-of-view meter scattering lidar at 22:14 on June 10, 2006, respectively. The cumulative laser pulses are 10,000. The solid line and the dotted line represent the high-level and low-level of the two wavelengths respectively. The high-level gating position of the 532nm wavelength is set at 3.57km, and the high-level gating position of the 1064nm wavelength is set at 1.56km.

Figure 7 is the comparison result of the 532nm actual atmospheric backscatter echo signal (solid line) and the numerical simulation calculation signal (dashed line) detected by the dual-wavelength dual-field-of-view m-scattering lidar. It can be seen that the range from 6km to 26km is completely the same . In the range from near the ground to 6km, due to the influence of human activities on the ground and atmospheric movement, the actual detected atmospheric backscatter echoes do not completely coincide with the calculated numerical simulation values, but the trends of the two curves are basically the same.

Figure 8 shows the linearity test results of the atmospheric backscatter echo signal of the dual-wavelength dual-field-of-view m-scattering lidar. The solid line is the ratio of the atmospheric backscatter echo signal detected by inserting and not inserting the 50% neutral attenuation film in front of the optical filter of the 532nm wavelength low-level channel, and the dotted line is the laser energy reduced by 75% and the laser energy normal The ratio of the atmospheric backscatter echo signal obtained by the time detection, it can be seen that the values of the two curves are about 0.5 and 0.75 respectively, indicating that the intensity of the atmospheric backscatter echo signal of the dual-wavelength dual-field-of-view m-scattering lidar has not changed. The saturation or distortion of the detector is caused, and the good linearity indicates the accuracy of the data obtained by the lidar detection.

Figure 9 is the vertical profile of the atmospheric aerosol extinction coefficient of the 532nm (solid line) and 1064nm wavelength (dashed line) detected by the dual-wavelength dual-field-of-view meter scattering lidar at 8:51 on December 29, 2006. The dotted line is Vertical profile of Rayleigh extinction coefficients for atmospheric molecules. It can be seen from the figure that the detection results of the extinction coefficients of the two wavelengths conform to the wavelength index relationship.

In order to test the performance and reliability of the dual-wavelength dual-field-of-view meter-scattering laser for detecting the extinction coefficient of atmospheric aerosols, on the night of January 10, 2007, a vertical measurement of the atmospheric aerosol extinction coefficient Profile detection.

Figure 10 shows the comparison results of the vertical profiles of the 532nm wavelength atmospheric aerosol extinction coefficient detected simultaneously by the dual-wavelength dual-field-of-view meter-scattering lidar (solid curve) and the polarized meter-scattering lidar (dashed curve). The dotted line in the figure is the vertical profile of the Rayleigh extinction coefficient of atmospheric molecules. Obviously, the vertical profiles of the tropospheric aerosol extinction coefficients detected by the two lidar systems are quite consistent, and the fine structures at the same altitude are also basically similar. The detection height of the vertical profile of the atmospheric aerosol extinction coefficient is greater than 10km during the day and greater than 15km at night.

Figure 11 shows the variation of the 532nm wavelength atmospheric aerosol extinction coefficient detected by the dual-wavelength dual-field-of-view meter-scattering lidar for 25 consecutive hours from 17:00 on January 9 to 18:00 on January 10, 2007. Figure 12 is a comparison of the change in atmospheric horizontal visibility detected by the dual-wavelength dual-field-of-view meter scattering lidar (solid) and Vaisala (hollow) within the same time period. It can be seen from the figure that the change trend of the atmospheric horizontal visibility detected by the two systems is basically the same. The atmospheric horizontal visibility dropped sharply from 17:00 to 18:00 on the 9th, from 18km to about 5km, and then declined slowly until the 10th. 9:00 reached the minimum value of 3km. Afterwards, the atmospheric horizontal visibility gradually increased until after 15:00 the atmospheric horizontal visibility gradually decreased. The dual-wavelength dual-field-of-view meter scattering lidar has the ability of automatic continuous observation.

Figure 13 shows the comparison results of the optical depth of the atmosphere detected by the dual-wavelength dual-field-of-view meter scattering lidar (solid) and the radiometer (hollow) within four hours on January 8, 2007. It can be seen that the detection results of the two systems totally agree. The dual-wavelength dual-field-of-view meter scattering lidar has the ability to detect the optical thickness of the atmosphere.

Claims (4)

1. the structure of a dual wavelength double-view field Mie scattering laser radar is characterized in that, comprises laser emission element, echoed signal receiving element, follow-up optical unit, acquisition of signal and collecting unit and control module; Described laser emission element comprises the Nd:YAG laser instrument, laser instrument is launched the laser pulse of 532nm and two wavelength of 1064nm, the optical axis parallel with the output optical axis of laser instrument is provided with the echoed signal receiving element, described echoed signal receiving element comprises diameter 200mm receiving telescope and diameter 400mm receiving telescope, is aligned in sequence with aperture, catoptron, eyepiece and beam splitter on the follow-up light path of diameter 400mm receiving telescope; Light path is divided into two-way behind the beam splitter, the 1064nm narrow band pass filter of leading up to connects photon counting detector, the output circuit of photon counting detector is provided with amplifier VT120, the output circuit of amplifier VT120 is provided with photon counting card MCS, and photon counting card MCS delivers to computing machine to the signal that collects and handles; Another road connects analog prober by the 532nm narrow band pass filter, the follow-up light path of analog prober is provided with amplifier 777, the output circuit of amplifier 777 is provided with the A/D data collecting card, and the A/D data collecting card is delivered to computing machine to the digital signal that collects and handled; Be aligned in sequence with aperture and eyepiece on the follow-up light path of diameter 200mm receiving telescope; Eyepiece sends signal to beam splitter by optical fiber, light path is divided into two-way behind the beam splitter, the 1064nm narrow band pass filter of leading up to connects photon counting detector, the output circuit of photon counting detector is provided with amplifier VT120, the output circuit of amplifier VT120 is provided with photon counting card MCS, and photon counting card MCS delivers to computing machine to the signal that collects and handles; Another road connects analog prober by the 532nm narrow band pass filter, the output circuit of analog prober is provided with amplifier 777, the output circuit of amplifier 777 is provided with the A/D data collecting card, and the A/D data collecting card is delivered to computing machine to the digital signal that collects and handled.

2. the detection method of dual wavelength double-view field Mie scattering laser radar is characterized in that, comprises laser emission element echoed signal receiving element, follow-up optical unit, acquisition of signal and collecting unit and control module; Described laser emission element adopts the Nd:YAG laser instrument, launches the laser pulse of 532nm and two wavelength of 1064nm simultaneously, and two receiving telescopes that are respectively 400mm and 200mm by diameter receive; The light that diameter 400mm receiving telescope receives is through aperture, by mirror reflects parallel ejaculation behind the eyepiece, is divided into two-beam through behind the beam splitter, and a branch of be 1064nm wavelength reflected light, and another bundle is a 532nm wavelength transmitted light; 98% 1064nm wavelength reflected light converts electric signal to by photon counting detector after by the filtering of 1064nm narrow band filter slice, amplifies the back through amplifier VT120 and is gathered by photon counting card MCS and deliver to the storage that computing machine carries out data, handles and shows in real time; 85% 532nm wavelength transmitted light carries out opto-electronic conversion by analog prober after by the filtering of 532nm narrow band filter slice, amplifies the back through amplifier 777 and delivers to the storage that computing machine carries out data by the collection of A/D data collecting card, handles and shows in real time; The light that diameter 200mm receiving telescope receives is through behind the aperture, converge coupling by eyepiece and deliver to optical fiber, be divided into two-beam through beam splitter, a branch of is 1064nm wavelength reflected light, another bundle is 532nm wavelength transmitted light, 98% 1064nm wavelength reflected light converts electric signal to by photon counting detector after by the filtering of 1064nm narrow band filter slice, amplifies the back through amplifier VT120 and is gathered by photon counting card MCS and deliver to the storage that computing machine carries out data, handles and shows in real time; 85% 532nm wavelength transmitted light carries out opto-electronic conversion by analog prober after by the filtering of 532nm narrow band filter slice, amplifies the back through amplifier 777 and delivers to the storage that computing machine carries out data by the collection of A/D data collecting card, handles and shows in real time; Computing machine is by the bright dipping of RS232 serial ports control laser instrument, the Q-Switch synchronizing signal of laser instrument output is by main wave producer, produce main ripple signal, wherein 4 the tunnel deliver to two photon counting card MCS and two A/D data collecting cards respectively, trigger pip as 4 analog input cards, other 2 the tunnel deliver to photon counting detector and the analog prober behind the diameter 400mm receiving telescope respectively, as the gate-control signal of two detectors.

3. the structure of dual wavelength double-view field Mie scattering laser radar according to claim 1 is characterized in that described diameter 400mm receiving telescope adopts small field of view, and its visual field size is regulated by aperture, receives upper atmosphere backscattering echo signal.

4. the structure of dual wavelength double-view field Mie scattering laser radar according to claim 2 is characterized in that described diameter 200mm receiving telescope adopts the big visual field that receives.

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