TOKYO, Feb 10 - Japan's Nikkei closed at a seven-week low on Tuesday as poor profits at Nikon Corp <7731.T> stemming from its digital camera division spurred selling in Olympus and other peers. The market was also hampered by a lack of fresh incentives ahead of a national holiday here on Wednesday and as participants looked ahead to U.S Federal Reserve Chairman Alan Greenspan's congressional testimony this week, traders said. The Nikkei average <.N225> ended down 0.36 percent at 10,365.40, its lowest since December 25. The broader TOPIX index <.TOPX> was up 0.05 percent at 1,025.25.//