Broad-band ultraviolet lens systems well-corrected for chromatic aberration

DETAILED DESCRIPTION We claim: 1.
A lens system comprising a first rigid lens element, a second rigid lens element and a liquid lens element, said liquid lens element being contained between said first and second rigid lens elements, said first and second rigid lens elements and said liquid lens element co-acting with each other to cause said lens system to have a Strehl ratio greater than 0.
60 over a continuous ultraviolet wavelength band from 0.
30 micron to 0.
45 micron and wherein said first and second rigid lens elements and said liquid lens element are configured and positioned with respect to each other according to a design form specified as follows:
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Surface
Radius Thickness
No.
(inches)
(inches) N.
sub.
d
V.
sub.
d
Material
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1 0.
8172 0.
0148 1.
768239
72.
01 Sapphire
2 0.
2509 0.
0250 1.
296386
100.
98 295990
(perfluorocarbon)
3 -0.
0840 0.
0148 1.
768239
72.
01 Sapphire
4 -0.
1077 1.
0594 Air
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where the surfaces of the lens elements are numbered consecutively from left to right along an optic axis, and where N.
sub.
d is the index of refraction at the wavelength of the sodium d spectral line and V.
sub.
d is the Abbe number at the same wavelength.
2.
A lens system comprising a first rigid lens element, a second rigid lens element and a liquid lens element, said liquid lens element being contained between said first and second rigid lens elements, said first and second rigid lens elements and said liquid lens element co-acting with each other to cause said lens system to have a Strehl ratio greater than 0.
60 over a continuous ultraviolet wavelength band from 0.
30 micron 0