Laser imaging of gases for concentration and location identification

A method of evaluating methane concentration within an area of space, the method comprising:

• directing at least one light wave from at least one light source toward an area of space to be analyzed in regard to methane concentration and through a windowpane comprising coatings on the windowpane, wherein the windowpane and the coatings together having a transmittance for light wavelengths that is different from a respective transmittance of an uncoated windowpane;
• modulating the light source between an on-resonance state, relative to the absorption spectrum of the methane, and an off-resonance state, relative to the absorption spectrum of the methane,
• receiving, at an imaging device, reflected light wherein the reflected light includes a first wavelength reflection corresponding to the on-resonance state and a second wavelength reflection corresponding to the off-resonance state of the light source;
• and
• calculating a ratio of reflected light signals at the first wavelength reflection and the second wavelength reflection to evaluate the methane concentration.