Optical: systems and elements – Having significant infrared or ultraviolet property – Lens – lens system or component
Reexamination Certificate
1999-05-03
2001-05-22
Henry, Jon (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
Lens, lens system or component
C359S791000
Reexamination Certificate
active
06236501
ABSTRACT:
This invention relates to an objective lens system for use in the thermal infra red waveband, particularly in the 8-12 micron waveband with a cooled or uncooled detection system.
According to the present invention there is provided an objective lens system for use with a detection system in the thermal infra red waveband, particularly in the 8-12 micron waveband, said objective lens system being light in weight whilst utilising Germanium lens elements and having high aperture to provide sensitivity, wherein the lens system comprises a single-element positively-powered objective lens, a single element positively-powered intermediate lens, and a single element negatively-powered field lens each mutually spaced apart along a common optical axis, and the field lens is arranged to flatten the field curvature of the lens system whilst the intermediate lens is arranged primarily to correct astigmatism and has an aspheric surface to correct the balance between oblique sagittal, tangential spherical aberration and high order astigmatism.
Preferably the objective lens is shaped to provide coma correction for the lens system, and has an aspheric surface to correct spherical aberration.
By virtue of the present invention each lens element is thin and of low mass despite being made of Germanium.
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Alston & Bird LLP
Henry Jon
Pilkington P-E Limited
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