Optical: systems and elements – Having significant infrared or ultraviolet property – Lens – lens system or component
Reexamination Certificate
1999-06-24
2001-06-12
Henry, Jon (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
Lens, lens system or component
Reexamination Certificate
active
06246517
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to lens systems for near infra-red imaging devices.
2. Description of Prior Art
With recent advances in charge coupled device (CCD) camera technology, it is now possible to fabricate focal plane detector arrays which are sensitive in the 1.5 to 2.55 micron spectral region. This spectral region features relatively good atmospheric transmission, and can capture energy from both reflective and thermally emissive objects at normal terrestrial temperatures. Most commercially available CCD camera lenses and night vision optics are optimized for use with wavelengths in the 0.6 to 1.0 micron band, and are not suitable for use with wavelengths in the 1.5 to 2.55 micron band. The lens materials are too lossy in the latter band and the corrections for chromatic and spherical aberrations are inadequate
SUMMARY OF THE INVENTION
An objective lens assembly for the 1.5 to 2.55 micron wavelength band including two positive lens elements separated by two negative lens elements. The first element is sapphire, the negative elements are fused quartz and the fourth element is zinc sulphide. This lens operates nominally at F/1.8 and provides a wide field of view with excellent resolution when imaging detector arrays of approximately 15 mm width and 25 microns or less pitch.
REFERENCES:
patent: 3305291 (1967-02-01), Snitchler
patent: 4147040 (1979-04-01), Altman
patent: 5446581 (1995-08-01), Jamieson
patent: 5940224 (1999-08-01), Zhang
Rudolf Kingslake, “Lens Design Fundamentals” Academic Press, London, 1978, pp. 243-250.
Bashore Alain L.
Henry Jon
Holford John E.
Lee Milton W.
The United States of America as represented by the Secretary of
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