Optical: systems and elements – Having significant infrared or ultraviolet property – Lens – lens system or component
Reexamination Certificate
1998-07-08
2001-03-27
Chang, Audrey (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
Lens, lens system or component
C359S356000, C359S350000, C359S717000
Reexamination Certificate
active
06208459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of optics. More specifically, the present invention provides a multi-spectral objective using a combination of magnesium oxide and calcium fluoride lenses to image visible and infrared wavelengths.
2. Related Art
Many imaging applications such as air-borne reconnaissance and tracking systems demand detection in both visible and infra-red spectrums. Typically, separate objectives must be used because no single objective lens system can accommodate multi-spectral images at both visible and infra-red wavelengths with adequate resolution. In particular, conventional refractive IR objectives disperse visible light, thereby, degrading image quality. Increasingly industry has been forced to less desirable reflective-type IR objectives.
What is needed is an objective lens system using refractive components that provides high-quality multi-spectral imaging in both visible and infrared spectrums.
SUMMARY OF THE INVENTION
The present invention is directed to a multi-spectral objective lens system. Two materials are used to fabricate lenses in the objective lens system: magnesium oxide (MgO) and calcium fluoride (CaF
2
). According to a first embodiment of the invention, a magnesium oxide lens and a calcium fluoride lens, in any order, form a doublet which images wavelengths in the visible and infra-red spectrums. Further embodiments include combinations of MgO and CaF
2
lenses in different objective lens designs including Petzval, inverted telephoto, and telephoto arrangements.
Thus, the inventors have discovered that the combination of magnesium oxide, only recently made available in a pure crystal form, and calcium fluoride can be used to fabricate an objective lens for imaging objects in both the visible and infra-red spectrums. The combination of magnesium oxide and calcium fluoride results in a super-achromatic condition, that is color correction across the visible and infra-red spectrums. This chromatically-corrected spectral range includes wavelengths between approximately 0.4 and 5.9 microns which covers medium-wave IR (MWIR), short-wave IR (IR), and the near-IR/visible windows.
The objective lens according to the present invention is well-suited for telescopes, reconnaissance planes, satellites, forward-looking IR (FLIR) and staring sensor systems, night-vision goggles, and other optic and/or electro-optic detection systems in visible and/or IR applications.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
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Dialog File 348 (European Patents) English Language Patent Abstract for EP 0683411 A1, Published Nov. 22, 1995, Base 1.
Coon Bryan
McGee, III John F.
Montulli Lou
Sherman Neil
Chang Audrey
Lockheed Martin Corporation
Sterne Kessler Goldstein & Fox PLLC
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