Apparatus and method of remote gas trace detection

a gas trace detection and apparatus technology, applied in the direction of optical radiation measurement, instruments, spectrometry/spectrophotometry/monochromators, etc., can solve the problems of high cost of opo-based lidar, prone to alignment problems, complex opo systems, etc., and achieve large losses.
US20030030001A1Inactive Publication Date: 2003-02-13GAS TECH INST
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
GAS TECH INST
Publication Date
2003-02-13
Estimated Expiration
Not applicable · inactive patent

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Abstract

This specification discloses a method and apparatus for the mobile and remote detection of a gas, such as methane, in the atmosphere. The apparatus includes a TDL based Light Detection and Ranging (LIDAR) driven at carrier frequency lying within the absorption line of the gas. The apparatus also drives the TDL with a modulation frequency to generate upper and lower sidebands in the output of the TDL and with a low ramp frequency to sweep the output of the TDL across twice the width of the pressure-broadened absorption line of the gas, preferably the first overtone absorption line in the case of methane detection. Suitable power for remote detection through use of the TDL is provided by a master oscillator / fiber amplifier transmitter has no moving or adjustable parts at all. An all-solid-state monolithic and integrated amplifier is achieved, which leads to a compact and virtually maintenance-free LIDAR system. The remote detection apparatus includes reference and calibration cells or chambers, and includes a light collector and detectors to detect the quantity and modulation of the light that passes the reference or calibration cells and that is received by the apparatus after reflection back toward the apparatus from an uncooperative target. The apparatus further includes a signal processor that applies a derivative spectroscopy technique, such as frequency modulation spectroscopy or wavelength modulation spectroscopy, to determine the presence of the gas in the atmosphere.
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Description

[0001] This is a continuation of U.S. patent application Ser. No. 09 / 488,453, filed January 2000.

[0002] This invention relates to the use of Light Detection and Ranging (LIDAR) to detect elements in the atmosphere remotely. More particularly, this invention relates to mobile use of modulated tunable diode lasers in order to sweep the laser wavelength through an absorption line of a gas such as methane in order to determine the presence of the gas in the atmosphere.

[0003] LIDAR systems operate somewhat like radar. LIDAR, however, directs laser light rather than radar waves at a particular target to detect the target. The laser light may be pulsed or relatively continuously generated, and it may be focused or collimated as desired to reach the desired end. Objects, particles, and gases can scatter and / or absorb the laser light. Thus, the measurement of the reflected light can provide information about the target or atmospheric constituents along the optical path. LIDAR data is derived...

Claims

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