Narrow Bandwidth Light Detector

Problem: Hot steel emits a blinding light that overwhelms conventional dimension sensing equipment employing optical sensors. Harris Instrument Corp. of Columbus, Ohio makes a conventional sensor to measure the width and position of material coming out of extruders and rollers, but the sensor can see only the colder, less emissive material. Harris needed a simple, economical detector that could see the edge of hot steel without being blinded by the light from the steel.

Solution:  Researchers from the Air Force Research Laboratory (AFRL) Sensors Directorate, under a Cooperative Research & Development Agreement (CRADA) with Harris Instrument, invented a solid state, high efficiency sensor that detects the edge of the hot steel while ignoring the light and heat radiated by it. Initial experiments in Bethlehem Steel's hot mill showed improvement over traditional sensors. AFRL Sensors Directorate has over 30 years experience developing solid state detectors. All aspects including device modeling, design, material growth, and fabrication were carried out in an AFRL facility.

Harris first described the problem to Wright Technology Network (WTN). WTN arranged the meeting, the CRADA, and the licensing agreement with AFRL.


  • Manufacturers and processors of hot metals will benefit by using these new detectors to measure bright hot features in situations requiring precise control.
  • The Air Force can benefit by using this technology in covert laser communicators that ignore ambient light signals.
  • The Air Force will also benefit by earning a royalty on commercial sales of the detectors.
  • Harris Instrument Corporation's product offers low-cost competition to Japanese steel mill technologies.

Current Status:

  • The U.S. Patent & Trademark Office has issued a patent (#5,621,238) on the new AFRL sensor.
  • The prototype sensor needs better sensitivity and can tolerate less side lobe attenuation. AFRL researchers may be able to alter the detector to have the required properties.
  • Harris Instrument's recent growth in the cold metal measurement market prevents it from developing instruments for the hot metal market.
  • WTN is negotiating to license the patent with a firm that does hot metal measurements.
If you have any questions about this Cooperative Research and Development Agreement or are interested in getting more information about technology transfer and CRADA projects, please contact Jim Singer at Wright Technology Network (937) 253-0217 or CRADA@wtn.org

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