Development of compact stand-off hazardous chemical detector based on Michelson interferometer

A compact stand-off chemical detector using a Michelson interferometer has been developed and is presented. Its size is only 104 × 183 × 108 mm3 and its weight is 2.5 kg, which makes it suitable for hand-held operation. This compact detector is a minimized version of the conventional Michelson interferometer. The housing for the interferometer was designed to be divided into two parts for minimization and convenient assembly. All the optics composing the interferometer were directly fastened to the housing. The moving mirror module in the Michelson interferometer was specially designed for the small size detector. Using a symmetrically positioned linear elastic plate, the tip and tilt angle of reflected light from the moving mirror were smaller than 8 arc sec during linear back-and-fourth motion without any active alignment feedback system, which results in low noise in the interference signal. The spectra of SF6 and NH3 were measured with changing concentration and the detection limit was determined to be 46.7 and 65.2 mg / m2, respectively. Additionally, outdoor measurement was demonstrated with a distance of about 1 km.