Portable remote laser sensor for methane leak detection

US4489239A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• William B. Grant · Altadena, US
• E. David Hinkley, Jr. · Glendora, US

Key dates

• Filing date: Sep 24, 1982
• Grant date: Dec 18, 1984
• Expiry date: Sep 24, 2002

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N2021/395
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A portable laser system for remote detection of methane gas leaks and concentrations is disclosed. The system transmitter includes first and second lasers, tuned respectively to a wavelength coincident with a strong absorption line of methane and a reference wavelength which is weakly absorbed by methane gas. The lasers are aimed at a topographical target along a system axis and the beams successively interrupted by a chopper wheel. The system receiver includes a spherical mirror for collecting the reflected laser radiation and focusing the collected radiation through a narrowband optical filter onto an optial detector. The filter is tuned to the wavelength of the two lasers, and rejects background noise to substantially improve the signal-to-noise ratio of the detector. The output of the optical detector is processed by a lock-in detector synchronized to the chopper, and which measures the difference between the first wavelength signal and the reference wavelength signal.