Meteorological observation lider system

• US 20040239913A1
• Filed: 07/15/2004
• Published: 12/02/2004
• Est. Priority Date: 02/21/2002
• Status: Active Grant

• Current Assignee: EKO Instruments Co., Ltd.
• Original Assignee: EKO Instruments Co., Ltd.
• Inventors: Kobayashi, Takao, Hua, Dengxin, Uchida, Kiyotaka, Hasegawa, Toshikazu
• Granted Patent: US 7,227,625 B2
• Time in Patent Office: Days
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/95 for meteorological use
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01W 1/00 Meteorology
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The present invention provides a LIDAR system for meteorological observation, in which LIDAR observations are performed based on observation light resulting from emission of laser light toward an object for observation, comprising a spectral analyzer, to spectrally analyze the above observation light into light in the wavelength region of the above laser light and light in wavelength regions other than this; first photodetection means for detecting light of a first frequency component which has passed through a first filter among the light of the wavelength range of the above laser light which has been spectrally analyzed; second photodetection means for detecting light of a second frequency component which has passed through a second filter among the light of the wavelength range of the above laser light which has been spectrally analyzed; third photodetection means for detecting light of the wavelength range of the above laser light which has been spectrally analyzed; and fourth photodetection means for detecting light of wavelength ranges other than the wavelength range of the above laser light which has been spectrally analyzed.

Claims

1. A lidar system for meteorological observation, in which pulsed laser light having a prescribed central frequency is emitted from a laser device and reflected light thereof is observed, comprising:

a spectral analyzer for spectrally analyzing reflected light for observation into light in the wavelength region of the laser light and light in wavelength regions other than the wavelength region of the laser light;

a first filter for selectively passing light centered on a first frequency component among the light of the wavelength region of the laser light which has been spectrally analyzed by said spectral analyzer;

first photodetection means for detecting the first frequency component light having passed through said first filter;

a second filter for selectively passing light centered on a second frequency component among the light of the wavelength region of the laser light which has been spectrally analyzed by said spectral analyzer;

second photodetection means for detecting the second frequency component light having passed through said second filter;

third photodetection means for detecting the light of the wavelength region of said laser light having been spectrally analyzed by said spectral analyzer; and

,

fourth photodetection means for detecting the light of wavelength regions other than the wavelength region of the laser light having been spectrally analyzed by said spectral analyzer.

2. The lidar system for meteorological observation according to claim 1, wherein light of the wavelength region of the laser light which has been spectrally analyzed by said spectral analyzer is passed at least two times through said first filter.

3. The lidar system for meteorological observation according to claim 1 or claim 2, wherein the first central frequency component to be passed by said first filter is set at a position closer to the prescribed central frequency of the laser light than the second central frequency component to be passed by said second filter.

4. The lidar system for meteorological observation according to claim 3, wherein the first central frequency to be passed by said first filter and the second central frequency to be passed by said second filter are respectively set on either side of and centered on the position of the frequency at which an amount of change in the spectral power with respect to temperature changes of the Rayleigh scattering spectrum according to a prescribed Rayleigh scattering spectrum function is minimum.

5. The lidar system for meteorological observation according to any of claims 1 through 4, wherein the first central frequency to be passed by said first filter is set to substantially 1.0 GHz, and that the second central frequency to be passed by said second filter is set to substantially 3.5 GHz.

6. The lidar system for meteorological observation according to any of claims 1 through 5, further comprising a monitoring device for monitoring output of laser light emitted from said laser device, and control means for controlling output of the laser light such that the central frequency of said laser light is constant, based on the output of the laser light monitored by said monitoring device.

7. The lidar system for meteorological observation according to claim 6, wherein said laser device has a seeder which supplies single-frequency light to a rod based on a prescribed applied voltage, and said control means controls the voltage applied to said seeder.

8. The lidar system for meteorological observation according to claim 7, wherein said monitoring device comprises:

a third filter which selectively passes light with a prescribed central frequency;

a first photodetector which detects laser light emitted from said laser device as a first monitored signal;

a second photodetector which detects light passed by said third filter as a second monitored signal; and

peak detection means which detects both a first peak value of spectral power, obtained by analysis of a spectrum based on the first monitored signal detected by said first photodetector, and a second peak value of spectral power, obtained by analysis of a spectrum based on the second monitored signal detected by said second photodetector.

9. The lidar system for meteorological observation according to claim 8, wherein said control means controls the voltage applied to said seeder such that, when ν

0 is the central frequency of light passed by said third filter and Δ

ν

is the half-maximum full width of the spectrum of light passed by said third filter, the central frequency of said laser light becomes equal to ν

0+Δ

ν

/2, based on the first peak value and second peak value detected by said peak detection means.

10. The lidar system for meteorological observation according to claim 9, wherein said control means controls the voltage applied to said seeder such that the absolute value of the rate of change of the ratio of said first peak value to said second peak value is maximum.

11. The lidar system for meteorological observation according to any of claims 1 through 10, wherein said laser device is an Nd:

YAG laser device, and that the third harmonic component of the laser light generated is extracted by a prescribed optical element and emitted.

12. The lidar system for meteorological observation according to any of claims 1 through 11, further comprising analysis means for performing prescribed analysis processing, based on response signals detected by said first through fourth photodetection means.

13. The lidar system for meteorological observation according to claim 12, wherein said analysis means determines the aerosol distribution state based on response signals detected by said first photodetection means and said third photodetection means.

14. The lidar system for meteorological observation according to claim 12 or claim 13, wherein said analysis means determines a prescribed response function and prescribed air temperature measurement sensitivity based on a prescribed Rayleigh scattering LIDAR equation based on response signals detected by said first photodetection means and said second photodetection means, and determines the atmospheric temperature distribution state based on said determined prescribed response function and prescribed air temperature measurement sensitivity.

15. The lidar system for meteorological observation according to any of claims 12 through 14, wherein said analysis means determines the water vapor distribution state, based on a prescribed Rayleigh scattering LIDAR equation based on response signals detected by said first photodetection means, and based on a prescribed Raman scattering LIDAR equation based on response signals detected by said fourth photodetection means.

16. The lidar system for meteorological observation according to any of claims 12 through 15, wherein said analysis means corrects said response signals based on noise data collected in advance.

17. A meteorological observation method using a LIDAR system for meteorological observation in which pulsed laser light having a prescribed central frequency is emitted from a laser device and reflected light thereof is observed, comprising the steps of:

spectrally analyzing the reflected light for observation into light in the wavelength region of said laser light and light in wavelength regions other than the wavelength region of the laser light by means of a spectral analyzer;

selectively extracting and detecting, by means of a first filter, light centered on a first frequency component among the light in the wavelength region of the laser light which has been spectrally analyzed by the spectral analyzer;

selectively extracting and detecting, by means of a second filter, light centered on a second frequency component among the light in the wavelength region of the laser light which has been spectrally analyzed by the spectral analyzer;

detecting light in the wavelength region of the laser light which has been spectrally analyzed by the spectral analyzer; and

,

detecting light in wavelength regions other than the wavelength region of the laser light which has been spectrally analyzed by the spectral analyzer.

18. A meteorological observation method using a LIDAR system for meteorological observation in which pulsed laser light having a prescribed central frequency is emitted from a laser device and reflected light thereof is observed, comprising the steps of:

collecting, as noise data, response signals measured in a state in which the laser light is cut off;

collecting, as observation data, response signals measured in a state in which the laser light irradiates an object of observation; and

,

correcting said observation data based on said collected noise data.