Canon Inc (7751.T) plans to buy network video surveillance leader Axis AB (AXIS.ST) for about 23.6 billion Swedish crowns ($2.83 billion), the biggest purchase ever for the Japanese company that is trying to expand beyond the shrinking camera market. Canon said it was launching a tender offer to buy all Axis shares for 340 crowns each, a premium of nearly 50 percent to their closing price of 226.90 on Monday. At 1008 GMT (05:08 a.m. EST), shares of Axis were up 48 percent at 336.70 crowns.