Apparatus and system for wide angle narrow-band optical detection in daylight

US7570426B2 · kind B2 · utility

Assignees

• THE JOHNS HOPKINS UNIVERSITY · US
• Eddy Corp. · US

Inventors

• Wayne Rodgers · Apple Valley, US
• Robert E. Erlandson · Columbia, US
• C. Bryon Hargis · Sykesville, US
• Neil Murphy · La Cañada Flintridge, US

Key dates

• Filing date: Jun 29, 2006
• Grant date: Aug 4, 2009
• Expiry date: May 5, 2027

Classification

• Technology area (CPC G): Physics
• CPC primary: G01J2003/1213
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Techniques for filtering light include, along a central optical axis, an entrance window; a first polarizer, a narrowband polarization-changing material, a second polarizer, and an exit window. The optical paths through the filter are substantively unscattered and pass through unstressed components between the polarizers. The polarization-changing material changes polarization for a narrow wavelength band on the order of about 0.01×10−9 meters and does not condense on optical windows and polarizers during the operational lifetime. An aspect ratio, defined by a distance from the entrance window to the exit window divided by an optical aperture for the entrance window, is less than 4/1. This filter thus transmits light substantively unattenuated in the narrow wavelength band up to a maximum acceptance angle greater than 5 degrees. Combined with optics and imaging detectors, it is suitable for wide area surveillance, including daylight surveillance for combustion like forest fire and missile plume.