[rollei_list] Obtaining U.S. Patents On-Line

Any United States patent ever issued, except for a few that were destroyed by fire, can be obtained on line from the United States Patent and Trademark Office at http://www.uspto.gov
Patents issued beginning in 1976 are available as full text and extensive searching is possible. They are also available as FAX tiff files. Those issued before 1976 are available only as FAX tiff images and no searching except by patent number is possible.
In order to view the tiff files a plug-in is necessary. A good one, available free, is Alternatiff, available at http://www.alternatiff.com Versions for both Internet Explorer and other browsers are available. There are pay for plug-ins which will convert the tiff to PDF if desired. On Windows machines the stored tiff filed can be viewed and printed using the fax/image viewer built into the operating system.
Viewers are available for Macintosh but I don't know which are the good ones. A web search should find out.
Patents are written in rather stilted language: they are legal, not scientific or technical documents. Some are written to state what is claimed clearly but to be confusing as to the actual application. With some practice one can become reasonably astute at deciphering them. Some will leave you feeling like you have seltzer water in your sinuses.
Lens patents are often not complete, especially older ones, where glass constants are not completely described. For this reason its often impossible to calculate the actual chromatic correction of lenses. So, even when the precscriptions are entered in a lens design program, it may not be able to completely calculate the performance of the design. In addition, some patents have errors so a little care is needed.
In any case, the patent office web site is a powerful resource. I don't know if any similar source for European or British patents, at least those older than about 1975.

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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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