Figure 1.

(a) System setup for the recording process. Light scattered on transmission through a sample interfered with a reference beam in a photorefractive crystal (PrC) over tens of seconds. A transmission measurement was made at the location indicated. (b) System setup for the playback process. A conjugate reference beam arrived at the PrC from the opposite direction and diffracted a conjugate beam toward the sample, retracing its path through the scattering material. The reconstructed beam was then focused to a spot and recorded at a CCD. A measurement of the phase conjugate power (OPC signal) was made at the location indicated.