2. Direct imaging for point targets Define the time reversal matrix R()@Po)p(p)a(点 k,k≠=1 a k, k) The point spread function kke In the well-resolved case Right singular vector Singular value (過学故时大学 A Direct Numerical Imaging Method National University of Defense TechnologyA Direct Numerical Imaging Method 2 2 0 0 0 0 0 0 ( ) , ( ) . T T k k k k k k k k P g g g P g g g w t w t = = v v v v v v 2. Direct imaging for point targets 8 Define the time reversal matrix ( ) 0 0 0 0 , 1 , , 1 ( ) ( ) ( )= ( , ) M T T T k k k k k k k k M k k k k k k R P P g g g g w w w t t ⅱ ⅱ ? ¢= ⅱ ¢= × L G å å v v v v @ @ x x In the well-resolved case The point spread function Right singular vector Singular value