Granted Patent
Utility
US 5,121,979 · App. 07/456,226
Diffractive multifocal optical device
Inventor:
Allen L. Cohen
Patented Case
View Patent ↗
Granted: Jun 16, 1992
Filed: Dec 22, 1989
Inventor
Allen L. Cohen
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.