| CPC G01N 21/3504 (2013.01) [G01N 21/01 (2013.01); G01N 2021/3513 (2013.01); G01N 2201/0636 (2013.01); G01N 2201/1211 (2013.01)] | 22 Claims |

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1. An optical differential path length gas detector, comprising:
a first light source configured to emit a first light centered at a first wavelength;
a second light source configured to emit a second light centered at a second wavelength; and
a mirror, disposed facing the first light source and the second light source, configured to reflect the second light emitted from the second light source onto the first light source, and to permit the first light emitted from the first light source and the second light after reflection by the first light source to pass through an aperture in the mirror that is facing the first light source.
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