Photoacoustic sensor
View Patent ↗A photoacoustic gas sensor, system and method is generally described. In some examples, a photoacoustic gas sensor includes a MEMS-based wavelength-selective optical modulator and a ring array of acoustic sensors. The MEMS-based optical modulator can be adapted to provide flexible wavelength selectivity such that a large number of chemical compounds may be detected. The ring array of acoustic sensors can be adapted to measure photoacoustically generated acoustic signals without the need for resonant enhancement of a photoacoustic cell of the gas sensor. In some examples, a unique uncorrelated and deterministic signal may be used to modulate each light wavelength of interest. Signal processing may be used that allows the simultaneous measurement of the absorption spectra of multiple optical wavelengths as well as the rejection of unwanted acoustic noise.
1. A photoacoustic sensor comprising:
an optical modulator configured to modulate an input light beam and produce modulated light that is directed to a sample region;
an array of acoustic sensors disposed in a ring configuration around the sample region, each of the array of acoustic sensors being substantially equidistant from the sample region, wherein each of the acoustic sensors is adapted to generate a signal responsive to acoustic enemy detected in the sample region; and
a controller coupled to the acoustic sensors and configured to detect one or more gases present in the sample region based on the signals generated by the acoustic sensors.
2. The photoacoustic sensor of claim 1 , wherein the controller is coupled to the optical modulator and adapted to control the modulation of the input light beam.
3. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises a dispersive element configured to separate the input light beam into wavelength components and is also configured to modulate the wavelength components non-uniformly.
4. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises a grating configured to separate the input light beam into wavelength components and is also configured to modulate the wavelength components non-uniformly.
5. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises a MEMS mirror array that is adapted to modulate the input light beam.
6. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises a first MEMS mirror array adapted to modulate a first wavelength component of the input light beam and a second MEMS mirror array adapted to modulate the same wavelength component of the input light beam.
7. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises one or more narrowband light sources, and a MEMS mirror array for modulating narrowband light from the one or more narrowband light sources to produce the modulated light that is directed to the sample region.
8. The photoacoustic sensor of claim 1 , wherein the optical modulator comprises an array of modulated narrowband light sources that produces the modulated light that is directed to the sample region.
9. A method of detecting one or more gases in a sample, the method comprising:
modulating an input light beam by separating the input light beam into wavelength components and modulating each of the wavelength components non-uniformly to produce modulated light;
directing the modulated light into a region containing the sample:
collecting acoustic signals from a plurality of acoustic sensors disposed about the region and substantially equidistant from the region; and
evaluating the collected acoustic signals to detect one or more gases present in the sample, wherein the acoustic signals result from interaction of the modulated light with at least a portion of the one or more gases located in the region.
10. The method of claim 9 , further comprising digitizing the acoustic signals, wherein the one or more gases detected in the sample are detected by evaluating the digitized acoustic signals.
11. The method of claim 9 , wherein one or more of modulating, directing, collecting, and/or detecting are carried out by a photoacoustic sensor having an optical modulator, an array of acoustic sensors, and a controller.
12. The method of claim 9 , wherein the modulated light is produced by an array of modulated narrowband light sources.
13. A method of detecting one or more gases in a sample, the method comprising:
modulating a first wavelength component of an input light beam using a first deterministic mudulation signal and modulating a second wavelength component of the input light beam using a second deterministic modulation signal to produce modulated light wherein the first deterministic modulation signal and the second deterministic modulation signal are uncorrelated to each other;
directing the modulated light into a region containing the sample;
collecting acoustic signals from a plurality of acoustic sensors disposed about the region and substantially equidistant from the region; and
evaluating the collected acoustic signals to detect one or more gases present in the sample, wherein the acoustic signals result from interaction of the modulated light with at least a portion of the one or more gases located in the region.
14. A method of detecting one or more gases in a sample, the method comprising:
modulating an input light beam to produce modulated light, wherein the input light beam is generated from one or more narrowband light sources, and modulated with a MEMS mirror array;
directing the modulated light into a region containing the sample;
collecting acoustic signals from a plurality of acoustic sensors disposed about the region and substantially equidistant from the region; and
evaluating the collected acoustic signals to detect one or more gases present in the sample, wherein the acoustic signals result from interaction of the modulated light with at least a portion of the one or more gases located in the region.
15. A photoacoustic sensor adapted to detect one or more gases from a sample located in a sample region of the photoacoustic sensor, the photoacoustic sensor comprising:
a grating configured to separate an input light beam into wavelength components;
a MEMS mirror array configured to modulate the wavelength components to produce modulated light components for the sample region;
an acoustic sensor disposed proximate a sample region through which the modulated light components pass and adapted to generate electrical signals responsive to acoustic signals detected in the sample region; and
a controller coupled to the acoustic sensor and configured to detect at least a portion of the one or more gases present in the sample region based on the electrical signals generated by the acoustic sensor.
16. The photoacoustic sensor of claim 15 , the MEMS mirror array comprising a first MEMS mirror array and a second MEMS mirror array, wherein the first MEMS mirror array is configured to modulate a first set of the wavelength components, and wherein the second MEMS mirror array is configured to modulate a second set of the wavelength components.
17. The photoacoustic sensor of claim 15 , wherein the controller is adapted to provide a unique uncorrelated deterministic modulation signal to the MEMS mirror array to modulate each of the wavelength components and wherein the controller is configured to detect the gases by digitizing and processing the electrical signals generated by the acoustic sensor.
18. The photoacoustic sensor of claim 17 , wherein the unique modulation signals comprise maximum-length-sequence-based modulation signals.
19. The photoacoustic sensor of claim 15 , wherein the input light beam is generated from one of a broadband visible light source, an IR light source, and a UV light source.