BEAVERTON, Ore., April 22 -- Display manufacturer Planar Systems Inc. announced that Jim Hurd, the company's president and CEO, intends to take a medical leave of absence. Effective May 13, Bill Walker, Planar's chairman, will become interim chief executive officer until Hurd returns to the company in late 1999. Hurd was recently diagnosed with leukemia with a favorable prognosis for treatment. He plans to undergo aggressive treatment starting in mid-May.Planar's three founders--Hurd, Chris King and John Laney--worked together at Tektronix where they developed what would become Planar's first product, the first commercial electroluminescent display. The three founded Planar in 1983, with the support of Tektronix Development Co.