WASHINGTON -(Dow Jones)- Reviving a patent lawsuit against Microsoft Corp. ( MSFT), a federal appeals court ruled Friday that a trial judge was too quick to throw out claims alleging that the software giant infringed six patents related to digital imaging.

The patents are owned by Research Corporation Technologies, Inc.

A federal trial judge in Arizona had thrown out RCT's patent claims, saying the company improperly hid information from the U.S. Patent and Trademark Office. The judge also found that Microsoft did not infringe the patents.

But the U.S. Court of Appeals for the Federal Circuit ruled Friday that the judge's decision to toss out the case was clearly erroneous.

The appeals court said the case should be reconsidered, and it ordered that a new trial judge should preside over the proceedings.

In January 2006, a federal district court in Arizona ruled three of six Research Corp. patents were unenforceable due to the patent applicant's " inequitable conduct" in withholding material information from the patent office with the intent to deceive. Three other patents were deemed invalid.

In its 2001 lawsuit, Research Corp., founded by two University of Rochester professors, claimed certain printing and computer display technologies in different versions of Windows had infringed on its patents. All the patents at issue relate to image halftoning technology used in computers and printers that break down pictures into dots of varying sizes.

Microsoft shares recently fell 2% to $25.21.

-By Brent Kendall, Dow Jones Newswires; 202-862-9222; brent.kendall@ dowjones.com

(Lauren Pollock contributed to this report.)

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  08-01-08 1224ET
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