Planar Systems Inc., a Beaverton, Ore., maker of flat panel display systems, has appointed Steve Flieder as vice president and general manager of its medical business, based in Waltham, Mass. Flieder has had management and senior roles at both GE Medical Systems and Siemens Medical Systems. Planar offers its healthcare customers medical display products including radiological imaging systems, flat panel displays certified for use in patient proximity, point-of-care workstations, display controllers and software development toolkits, rugged display modules for integration in portable medical instruments and flat panel monitors for administrative needs.   . . .   Laserscope, a San Jose, Calif.-based developer of medical lasers and advanced fiber optic devices, was named supplier of the year for 2002 by the McKesson Primary Care Div. Laserscope sales through McKesson grew 102 percent in 2002 over 2001. McKesson is the exclusive distributor of Laserscope's aesthetic and cosmetic medical laser products.   . . .   Shares of the Essex Corp. began trading on the American Stock Exchange yesterday under the symbol "EYW". Essex, based in Columbia, Md., provides expertise in optical and signal process development to commercial, defense and intelligence customers.