Optical: systems and elements – Having significant infrared or ultraviolet property – Lens – lens system or component
Reexamination Certificate
2000-07-07
2002-08-27
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
Lens, lens system or component
C359S356000, C359S565000, C359S581000, C359S589000
Reexamination Certificate
active
06441956
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to optical elements operating in transmission in the infrared spectrum, and the subject of the invention is the creation of optical elements of this type, the main characteristic of which lies in the fact that they are provided with a high-density-polyethylene coating layer.
High-density polyethylene (HDPE) is a polymeric material which presents high transmittance of infrared radiation (approximately 80% for a thickness of 0.5 mm). The index of refraction is low, namely, approximately 1.5 both in the LWIR range (from 8 to 14 micron) and in the MWIR range (from 3 to 5 micron). It moreover presents high impermeability.
HDPE is therefore suited for the production of optical elements for focusing IR radiation, provided that the thickness of the material is kept small (less than 1 mm). For this reason, HDPE is commonly used for the production of Fresnel lenses or refractive microlenses having a very small diameter (and hence a small depth). It is not, instead, conceivable to produce HDPE refractive lenses of greater thickness on account of absorption.
SUMMARY OF THE INVENTION
As already specified above, the subject of the present invention is represented by the use of HDPE not as a basic material for IR optical elements, but as a coating for IR optical elements made of some other material (for example, hygroscopic salt, semiconductor materials, fluorides, chalcogenides, silver halides, and others), exploiting the unique properties of HDPE, at the same time keeping the thickness reduced.
REFERENCES:
patent: 4533593 (1985-08-01), Miyata et al.
patent: 5091730 (1992-02-01), Cardiasmenos et al.
patent: 5151826 (1992-09-01), Pasco
Lambertini Vito
Perlo Piero
Repetto Piermario
Sinesi Sabino
Assaf Fayez
C.R.F. Societa Consortile per Azione
Spyrou Cassandra
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