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Optical Systems
The Ultraviolet Imager Optical system uses a high
speed (f/2.9) three mirror off axis design resulting in a circular
8 degree full field of view. This design provides an unobscured
optical aperture, excellent baffling, flat filed, provision for
optical filter insertion and general compactness. Each of the
three mirrors are portion of a conic section and all share a
common optical axis. The mirrors made of aluminum which underwent
an extensive thermal cycling, plating, machining, and polishing
process. They are overcoated with a far ultraviolet reflective
MgF2/Al coating. In order to minimize scattering, very smooth
surfaces are required. The surface roughness achieved on these
mirrors is less than 20 Angstroms rms. Internal baffling is incorporated
to further reduce stray light scattering. The image surface is
essentially flat over the 8 degrees diameter of the filed of
view (an 18 mm diameter image plane).
For more information on the optical design
of the UVI see the following paper:
- Johnson, R. B., 'Wide Field of View Three-Mirror
Telescopes Having a Common Optical Axis', Opt. Eng., vol. 27,
p. 1046, (1988).
- The optical design for the UVI was conceived
by Barry Johnson. Refinements in the optical design were made
by Drs. M. Krim and A. Nonemacher of Hughes Danbury. The final
optical design was done by Dr. Chen Feng while at the Center
for Applied Optics fo the the University of Alabama in Huntsville.
Photographs
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