Granted Patent
Utility
US 5,073,021 · App. 07/324,827
Bifocal ophthalmic lens constructed from birefringent material
Inventor:
Joseph Marron
Patented Case
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Granted: Dec 17, 1991
Filed: Mar 17, 1989
Inventor
Joseph Marron
Assignee (at issue)
Environmental Research Institute
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.