Chemical sensing with noise pre-compensation
AssigneeCeLight, Inc.
InventorPak Shing Cho
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Abstract
This invention relates generally to the systems and methods for chemicals detection such as explosives and others, and more particularly to optical devices and the methods of their use based on sensing of gases and residue materials. This sensing includes detection of optical spectrum and relative concentration of the chemical followed by the chemical identification based on these data. The sensing is based on photothermal interferometry method modified by implementation of coherent optical detection using a balanced receiver, where the incoming optical signal is mixed with a local oscillator beam. An additional phase shift is embedded in the local oscillator beam for adaptively negating the background noise in the incoming optical signal thus improving the system performance.
Claims20
A photo-thermal interferometric system that provides information about a chemical at a remote location, comprising:
- a first light source assembly that emits a first beam, the first beam having at least one wavelength that interacts with the chemical and changes a refractive index of the chemical;
- a second light source that produces a second beam, the second beam interacting with the chemical resulting in a third beam with a phase change that corresponds with the change of the refractive index of the chemical;
- and
- a detector system positioned remote from the chemical to receive at least a portion of the third beam, the detector system providing information on a phase change in the third beam relative to the second beam that is indicative of at least one of, absorption spectrum and concentration of the chemical;
- wherein the detector system includes one pair of balanced photodetectors.
A method for determining information about a chemical at a remote location, comprising:
- directing a first beam to a remote location where a chemical is present, the first beam interacting with the chemical and changing a refractive index of the chemical;
- directing a second beam that interacts with the chemical, forming a third beam having a phase change relative to the second beam that corresponds with the change of a refractive index of the chemical;
- receiving at least a portion of the third beam at a detection system positioned remote from the chemical;
- measuring a phase shift of the third beam that is induced by the first beam and is indicative of at least one of absorption spectrum and concentration of the chemical, and
- wherein the detection scheme is operating in homodyne regime.
Dependencies are inferred from the claim text.