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The Radon-Wigner Transform     111


               and therefore Eq. (4.8) can be reformulated as
                             ⎧
                                +∞

                             ⎪
                             ⎪          x      x
                             ⎪
                             ⎪    g x,     −       dx    for    = 0,
                             ⎪
                             ⎪         sin    tan                 2
                             ⎪
                             ⎪
                             ⎪ −∞
                             ⎪
                             ⎪
                             ⎪ +∞
                             ⎪
                             ⎨
                    R g (x   ,  ) =  g (x   ,y) dy       for   = 0  (4.11)
                             ⎪
                             ⎪
                             ⎪ −∞
                             ⎪
                             ⎪
                             ⎪ +∞
                             ⎪
                             ⎪
                             ⎪
                             ⎪
                             ⎪    g (x, x   ) dx         for   =
                             ⎪
                             ⎪                                  2
                             ⎩
                               −∞
               Thus, when we consider as projected function W f (x,  ), we can define
               the generalized marginals as the Radon transform of this WDF, namely,
                                              +∞

                                      (x   ,  ) =
                 R{W f (x,  ),x   ,  }= R W f   W f (x,  ) d
                                             −∞
                                   +∞

                                =    W f (x   cos   −   sin  ,x   sin   +   cos  ) d
                                  −∞
                                  ⎧
                                    +∞

                                  ⎪
                                  ⎪           x      x
                                  ⎪
                                  ⎪    W f  x,    −      dx  for    = 0,
                                  ⎪
                                  ⎪          sin    tan               2
                                  ⎪
                                  ⎪
                                  ⎪ −∞
                                  ⎪
                                  ⎪
                                  ⎪ +∞
                                  ⎪
                                  ⎨
                                =      W f (x   ,  ) d       for   = 0
                                  ⎪
                                  ⎪
                                  ⎪ −∞
                                  ⎪
                                  ⎪
                                  ⎪ +∞
                                  ⎪
                                  ⎪
                                  ⎪
                                  ⎪
                                  ⎪    W f (x, x   ) dx      for   =
                                  ⎪
                                  ⎪                                 2
                                  ⎩
                                    −∞
                                                                    (4.12)
               where, in the last expression, we have explicitly considered the equa-
               tions for the integration lines in the projection. In terms of the original
               signal, this transform is called its Radon-Wigner transform. It is easy
               to show that
                                          +∞ +∞

                                                                  x
                      (x   ,  ) = RW f (x   ,  ) =  f  x   cos   −   sin   +
                   R W f
                                                                  2
                                         −∞ −∞

                                                   x
                              × f  ∗  x   cos   −   sin   −
                                                   2
                              × exp[−i2 (x   sin   +   cos  )x ] dx d   (4.13)
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