sealed beam

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sealed beam (plural sealed beams)

  1. (technology) A type of electric lamp for producing a beam of light in which the filament is sealed inside a unit consisting of the reflector and lens so as to ensure the alignment of the beam and to protect the reflector from becoming dirty or tarnished.
    • 1940, Ralph A. Richardson, Optics and Wheels, General Motors Corporation, p. 25
      The new Sealed Beam Headlights are designed to maintain substantially their initial efficiency throughout their life.