Passive millimeter wave radiometer system for calibration of infrared cameras
AssigneesNational Technology & Engineering Solutions of Sandia, LLC, Massachusetts Institute of Technology
InventorsRyan D. Murphy, Eric C. Forrest, Paul P. Woskov, Joshua Stanford
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Abstract
An apparatus for accurate measurement of surface and sub-surface temperatures of an object from a distance without contacting the object is provided. Illustrative embodiments provide for simultaneous measurement of thermal emission and emissivity in the mm-wave regime thereby enabling real-time non-contact measurement of emissivity. Corrected temperatures for the object which may be used for calibration of infrared thermographic cameras are determined from the measurement of emissivity.
Claims20
A light wave radiometer configured to measure light received from a source, the light wave radiometer comprising:
- a window disposed in a primary light path to pass focused light from the source;
- a parabolic mirror disposed in the primary light path from the window;
- a waveguide disposed in the primary light path from the parabolic mirror, the waveguide configured to collect and guide the focused light along the waveguide;
- an optical chopper disposed in the primary light path from the parabolic mirror and the waveguide, the optical chopper disposed at an angle relative to an axis of the primary light path such that the optical chopper periodically allows the focused light to pass into a secondary light path and a tertiary light path;
- a first radiometer receiver disposed in the secondary light path;
- a second radiometer receiver disposed in the tertiary light path;
- a first lock-in amplifier electrically connected to the first radiometer receiver and configured to generate a first signal in response to receiving the focused light in the secondary light path;
- and
- a second lock-in amplifier electrically connected to the second radiometer receiver and configured to generate a second signal in response to receiving the focused light in the tertiary light path.
A method of measuring a temperature of a source using a light wave radiometer configured to measure light received from the source, the light wave radiometer comprising:
- a window disposed in a primary light path to transmit focused light from the source;
- a parabolic mirror disposed in the primary light path from the window;
- an optical chopper disposed in the primary light path from the parabolic mirror and a waveguide, the optical chopper disposed at an angle relative to an axis of the primary light path such that the optical chopper periodically allows the focused light to pass into a secondary light path and a tertiary light path;
- a first radiometer receiver disposed in the secondary light path;
- a second radiometer receiver disposed in the tertiary light path;
- a first lock-in amplifier electrically connected to the first radiometer receiver and configured to generate a first signal in response to receiving light in the secondary light path;
- and a second lock-in amplifier electrically connected to the second radiometer receiver and configured to generate a second signal in response to receiving light in the tertiary light path, the method comprising:
- receiving the light from the source into the window to form the primary light path;
- collecting the light through the window and focusing the light using the parabolic mirror;
- chopping the light with the optical chopper into a secondary light beam and the tertiary light beam, thereby directing the light into the secondary light path and the tertiary light path;
- receiving the secondary light beam at the first lock-in amplifier and generating the first signal with the first lock-in amplifier;
- receiving the tertiary light beam at the second lock-in amplifier and generating the second signal with the second lock-in amplifier;
- combining the first signal and the second signal with a computer to form a combined signal;
- and
- calculating an emissivity and corrected temperature of the source based on the combined signal.
Dependencies are inferred from the claim text.