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2. Corrective Optics Space Telescope Axial Replacement

   en.wikipedia.org/wiki/Corrective_Optics_Space...

   The Corrective Optics Space Telescope Axial Replacement (COSTAR) is an optical correction instrument designed and built by NASA. It was created to correct the spherical aberration of the Hubble Space Telescope ' s primary mirror , which incorrectly focused light upon the Faint Object Camera (FOC), Faint Object Spectrograph (FOS), and Goddard ...

3. Flat lens - Wikipedia

   en.wikipedia.org/wiki/Flat_lens

   A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. [1] The term is also used to refer to other lenses that provide a negative index of refraction. [2] Flat lenses require a refractive index close to −1 over a broad angular range.

4. Fluorescent lamp - Wikipedia

   en.wikipedia.org/wiki/Fluorescent_lamp

   A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow.

5. Flashlight - Wikipedia

   en.wikipedia.org/wiki/Flashlight

   For a given size of light source, a larger reflector or lens allows a tighter beam to be produced, while capturing the same fraction of the emitted light. Some flashlights use Fresnel lenses, which allow the weight of the lens to be reduced. The reflector may have a flat transparent cover to keep out dirt and moisture, but some designs have a ...

6. Fluorescent-lamp formats - Wikipedia

   en.wikipedia.org/wiki/Fluorescent-lamp_formats

   Cross section of a typical fluorescent lamp with and without a reflector. Some lamps have an internal opaque reflector. Coverage of the reflector ranges from 120° to 310° of the lamp's circumference. Reflector lamps are used when light is only desired to be emitted in a single direction, or when an application requires the maximum amount of ...

7. Diffuser (optics) - Wikipedia

   en.wikipedia.org/wiki/Diffuser_(optics)

   In optics, a diffuser (also called a light diffuser or optical diffuser) is any material that diffuses or scatters light in some manner to transmit soft light.Diffused light can be easily obtained by reflecting light from a white surface, while more compact diffusers may use translucent material, including ground glass, teflon, opal glass, and greyed glass.