Rapidly tuneable diode lidar for methane detection

A gas detection system, comprising:

• a diode laser operable to output a continuous wave output radiation;
• a control element operable to modulate a drive current for the diode laser and tune a wavelength of the diode laser continuously within a first wavelength spectrum, the first wavelength spectrum corresponding to at least a first spectral feature associated with an absorption spectrum of a gas to be detected;
• a modulator operable to apply a first output modulation to the output radiation from the diode laser;
• an optical transceiver system operable to transmit the modulated output radiation from the diode laser in a scan having at least two dimensions towards a first target location, and to collect scattered diode laser radiation and direct it to a detector, the scattered diode laser radiation having been at least partially modified by the, or each, gas between the gas detection system and the first target location;
• a detector operable to receive the scattered diode laser radiation collected by the optical transceiver system and provide one or more signals indicative of properties of the received scattered diode laser radiation;
• and
• a processing element operable to process the provided signals by (i) correlating the received scattered diode laser radiation with the transmitted output radiation to create one or more correlated data sets, and (ii) forming an area scan of target locations to determine concentration of the gas between the gas detection system and each target location, wherein multiple correlated data sets corresponding to fixed spatial points are used for determining concentration of the gas for each target location.