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US 12,663,312 B2Granted
Pixel scale Fabry Perot filter array for chemical agent vapor detection
AssigneeMassachusetts Institute of Technology
InventorWilliam Lawrence
Life of this patent
Estimating the term…
Abstract
Fabry-Pèrot filters having different cavity thicknesses are formed in arrays on a substrate for spectral sensing. The filter array can be coupled to a detector array to make a compact, low size, weight and power spectral sensor that detects spectral information in a scene viewed by the detector array. The spectral sensor can be used in a compact spectrometer to detect the presence of harmful chemical vapors.
Claims15
A spectral sensor comprising:
- a first substrate;
- an array of optical filters formed on the first substrate, each optical filter having:
- a first mirror formed on the first substrate;
- a second mirror spaced apart from the first mirror and in optical communication with the first mirror;
- and
- an etalon cavity formed between the first mirror and the second mirror;
- a second substrate;
- an array of long wavelength infrared (LWIR) detectors formed on the second substrate, the array of LWIR detectors in optical communication with the array of optical filters;
- and
- an optical element, disposed between a field-of-view of the spectral sensor and the array of optical filters, to homogenize emissions from the field-of-view across all of the array of LWIR detectors in the spectral sensor and eliminate a spatial dependence of the field-of-view in a spectral domain for the spectral sensor such that the array of LWIR detectors does not image the field-of-view, wherein:
- the array of optical filters includes at least 10 optical filters for which the etalon cavities of the 10 optical filters have different thicknesses such that the 10 optical filters have different transmission functions or different reflectivity functions,
- the etalon cavities of the 10 optical filters having the different thicknesses are all etched from a same layer of material on the first substrate, and
- the spectral sensor is assembled with the array of optical filters, the optical element, and the array of LWIR detectors in a package without Peltier cooling, the package having a size and weight to mount on an unmanned aerial vehicle weighing less than 20 pounds and to be flown by the unmanned aerial vehicle.
10 more elements
A method of making a spectral sensor, the method comprising:
- illuminating a grayscale photomask to expose a photoresist and pattern an array of etalon cavities for Fabry-Pèrot filters, wherein the photoresist is deposited over an etalon layer on a substrate;
- developing the photoresist such that the photoresist has at least 10 different thicknesses over the etalon layer;
- etching the photoresist and at least a portion of the etalon layer to pattern the array of etalon cavities, wherein the array of etalon cavities includes at least 10 etalon cavities having different thicknesses;
- forming an array of the Fabry-Perot filters from the array of etalons;
- disposing the array of Fabry-Perot filters adjacent to an array of LWIR detectors;
- disposing an optical element between a field-of-view of the spectral sensor and the array of etalon cavities, wherein the optical element homogenizes emissions from the field-of-view across all of an array of LWIR detectors for the spectral sensor and eliminates a spatial dependence of the field-of-view in a spectral domain for the spectral sensor such that the array of LWIR detectors does not image the field-of-view;
- and
- assembling the optical element, the array of Fabry-Perot filters, and the array of LWIR detectors in a package without Peltier cooling, the package having a size and weight to mount on an unmanned aerial vehicle weighing less than 20 pounds and to be flown by the unmanned aerial vehicle.
5 more elements
Dependencies are inferred from the claim text.