r lenses. In 1822 Augustine Fresnelmade a lens whose outer surface, instead of being con-tinuously spherical, was made in steps or concentriczones. The thickness of the lens was thus reducedto a minimum, thereby diminishing the loss of lightby absorption in passing through the glass.… … Operating Mechanism for Revolving: Lantern. lens—a lens having the shape of the solid generatedby revolving the middle vertical section of the ordi-nary Fresnel lens about a vertical axis. The cylin-drical lens bends the rays to a horizontal plane, pro-ducing an equal distribution of light in a…
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