Granted Patent
Utility
US 4,155,734 · App. 05/849,275
Preparation of photochromic gradient lenses
Inventor:
David A. Krohn
Patented Case
View Patent ↗
Granted: May 22, 1979
Filed: Nov 7, 1977
Inventor
David A. Krohn
Assignee (at issue)
American Optical Corporation
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.