Reverse photoacoustic standoff spectroscopy
First Claim
1. A standoff spectroscopy system comprising:
- a light source that emits pulsed light;
a target that is illuminated by the light source, wherein at least some of the pulsed light at the target is scattered, reflected, or refracted;
a vibratory detector that measures the scattered pulsed light from the target, wherein a photoacoustic wave is produced on a surface of the detector creating a mechanical vibration of the detector that is used to measure the intensity of the scattered pulsed light as the optical frequency of the light is varied; and
a collection optic that focuses the scattered, reflected, or refracted light onto the vibratory detector;
wherein the target is located away from the light source and the detector in the standoff spectroscopy system.
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Abstract
A system and method are disclosed for generating a reversed photoacoustic spectrum at a greater distance. A source may emit a beam to a target and a detector measures signals generated as a result of the beam being emitted on the target. By emitting a chopped/pulsed light beam to the target, it may be possible to determine the target'"'"'s optical absorbance by monitoring the intensity of light collected at the detector at different wavelengths. As the wavelength of light is changed, the target may absorb or reject each optical frequency. Rejection may increase the intensity at the sensing element and absorption may decrease the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.
54 Citations
24 Claims
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1. A standoff spectroscopy system comprising:
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a light source that emits pulsed light; a target that is illuminated by the light source, wherein at least some of the pulsed light at the target is scattered, reflected, or refracted; a vibratory detector that measures the scattered pulsed light from the target, wherein a photoacoustic wave is produced on a surface of the detector creating a mechanical vibration of the detector that is used to measure the intensity of the scattered pulsed light as the optical frequency of the light is varied; and a collection optic that focuses the scattered, reflected, or refracted light onto the vibratory detector; wherein the target is located away from the light source and the detector in the standoff spectroscopy system. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A standoff spectroscopy system comprising:
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a quantum cascade laser light source that emits pulsed light; a target that is illuminated by the light source;
wherein at least some of the pulsed light at the target is scattered; anda quartz crystal tuning fork distanced from the target, the quartz crystal tuning fork being used as a detector that measures the scattered pulsed light from the target, wherein the scattered pulsed light from the target produces a photoacoustic wave on the surface of the detector creating a mechanical vibration of the detector. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A system for standoff spectroscopy comprising:
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a target; a source array comprising a plurality of sources that each emit a pulsed light beam with different pulse frequencies onto the target at a predetermined frequency; and a detector array located a distance from the target, the detector array comprising a plurality of detectors that each have a predetermined resonant frequency, wherein the resonant frequency for each of the detectors corresponds with the predetermined frequency from one of the sources, further wherein each of the detectors measures, on a surface of that detector, an optical scattering, reflection, or refraction by the target of the pulsed light beam from the corresponding one of the sources. - View Dependent Claims (17, 18, 19, 23)
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20. A system for standoff spectroscopy of a target comprising:
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a quantum cascade laser array that emits pulsed light beams onto the target; a collection optic that receives scattered, reflected, and/or refracted light from the pulsed light beams being rejected by the target; and a quartz crystal tuning fork array that receives the scattered, reflected, and/or refracted light from the collection optic and generates a vibration on each of the quartz crystal tuning forks in the array. - View Dependent Claims (21, 22, 24)
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Specification