The scales of justice have tipped slightly in favor of Cognex Corp. and the more than 600 other companies that are contesting patent claims by the Lemelson Medical, Education & Research Foundation, Limited Partnership, in Incline Village, Nev.In late January, the US Court of Appeals for the Federal Circuit ruled that Cognex, based in Natick, Mass., could raise the doctrine of patent prosecution laches as one of its defenses against the Lemelson Partnership's infringement claims. The doctrine bars patentees from enforcing claims if there was an unreasonable delay in seeking the claim from the Patent and Trademark Office.Jerome Lemelson, the fourth- most-patented American, applied for several machine vision patents in the 1950s and 1960s and extended and modified them over the 30 years that the Patent Office took to grant them. Then he approached machine vision and bar-code users for license fees, claiming they were violating the patents.The ruling by the Court of Appeals permits Cognex to argue that Lemelson's modifications during the 30-year process constitute an unreasonable delay, rendering his patents unenforceable. If Cognex's laches defense succeeds in trial court, the vast majority of the foundation's patent claims could be deemed unenforceable.Legal experts have estimated that patents assigned to the Lemelson foundation could provide it with more than 600 licensees and revenues of about $1 billion. Most of those cases are on hold, awaiting the results of the Cognex lawsuit, which is expected to go to trial in August.