Cadtrak Corp, San Mateo, California has filed a suit against Western Digital Corp and its Western Digital Imaging subsidiary alleging infringement of patents on functions in raster graphics devices: Western Digital said that Cadtrak’s claim lacks merit because it holds a broad licence under the two Cadtrak patents covering both chips and circuit board products; it noted that in a lawsuit between Cadtrak and Commodore Business Machines, Commodore is asking the court to declare the patents invalid.