Rapidly tuneable diode lidar

A gas detection device, comprising:

• a diode laser operable to output first output radiation, wherein the first output radiation comprises a continuous wave output;
• a control element operable to tune a first emission wavelength of the first output radiation from the diode laser continuously within a first wavelength spectrum at a rate of at least 1 μm per second by modulating a drive current of the diode laser with a first drive current modulation having a frequency of at least 100 kHz, the first wavelength spectrum comprising a first spectral feature associated with at least part of a gas absorption spectrum of at least one gas to be detected;
• a modulator operable to apply a first output modulation to the first output radiation from the diode laser, the first output modulation comprising a first plurality of binary pulses;
• an optical transceiver system operable to transmit the modulated first output radiation from the diode laser in a three-dimensional scan towards a first target location using optical guide elements, and to collect scattered diode laser radiation and direct it to a detector using at least one of said optical guide elements, the scattered diode laser radiation having been at least partially modified by the, or each, gas between the gas detection device and the first target location;
• a detector operable to receive the scattered diode laser radiation collected by the optical transceiver system;
• and
• a processing element operable to process the received scattered radiation by (i) correlating the received scattered diode laser radiation with the transmitted first output radiation to create one or more correlated data sets, and (ii) forming an area scan of target locations to determine concentration of the at least one gas between the gas detection device 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.

An optical device,

• wherein the optical device is operable to output first output radiation from a diode laser,
• wherein the first output radiation comprises a continuous wave output;
• wherein the optical device is operable to tune a first emission wavelength of the first output radiation continuously within a first wavelength spectrum at a rate of at least 1 μm per second by modulating a drive current of the diode laser with a first drive current modulation having a frequency of at least 100 kHz, the first wavelength spectrum comprising a first spectral feature associated with a first characteristic of a first substance;
• wherein the optical device is operable to apply a first output modulation to the first output radiation;
• wherein the optical device is operable to transmit the modulated first output radiation through optical guide elements in a three-dimensional scan towards a first target location, and to receive scattered radiation from the target location and direct it to a detector using at least one of said optical guide elements, the scattered radiation having been at least partially modified by the first substance in the first target location;
• and
• wherein the optical device is operable to process the received scattered radiation by (i) correlating the received scattered radiation with the transmitted first output radiation to create one or more correlated data sets;
• and (ii) forming an area scan of locations in a first target area to determine concentration of the first substance between the optical device and the locations,
• wherein multiple correlated data sets corresponding to fixed spatial points are used for determining the concentration of the first substance for each of the locations.