Accession Number : AD0366587

Title :   OPERATION CROSSROADS REPORT OF BUREAU OF SHIPS INSTRUMENTATION GROUP SECTION XI. ICAROSCOPES.

Corporate Author : JOINT TASK FORCE ONE WASHINGTON D C

Report Date : 1947

Pagination or Media Count : 17

Abstract : The Icaroscope is an optical instrument that allows the simultaneous observation of dazzling and ordinary objects. This is accomplished through the use of the decay properties of the luminosity of a phosphor screen which gives a low contrast between a bright and weak light source. The optical system consists of a 12 in. focal length objective lens which forms a real image on a phosphor screen. Light from the source is intermittently admitted to the screen through a rotating shutter illuminating the phosphor. A second shutter rotating out of phase with the first discloses the screen to the observer through a roof prism and eyepiece 1/100 of a second after illumination. This delay between illumination and observation of the screen is sufficient to allow proper decay of luminosity and still retain a visible image. As the luminosity of bright light decays at a faster rate than that of a weak light, it is possible to observe two lights of different intensity at a reduced contrast. Because of this property, Icaroscopes were used during the initial period of the blast to observe any phenomena that would be indiscernible to the eye with or without filters. (Author)

Descriptors :   (*OPTICAL EQUIPMENT, PHOSPHORESCENT MATERIALS)

Subject Categories : Optics
      Nuclear Explosions and Devices(non-military)
      Cartography and Aerial Photography

Distribution Statement : APPROVED FOR PUBLIC RELEASE