Real-time holographic interferometry with double two-wave mixing in photorefractive crystals.

We present a real-time holographic interferometer for which two reference waves of different phases are created by two-wave mixing with a stationary signal wave in a photorefractive crystal. These waves are reconstructions of the stationary signal wave and interfere with the momentary (changing) signal wave in the manner of a holographic real-time interferometer. A fast change (phase or intensity) of the signal wave leads to different intensity changes in both interferograms that are jointly used for evaluation.

Giant momentary readout produced by switching electric fields during two-wave mixing in sillenites.

We show theoretically and experimentally that switching an applied square-wave field produces strong and short pulses of the outgoing signal during two-wave mixing in sillenite crystals. These pulses originate from the strong effect of the field on the optical eigenmodes and can be used in new optical schemes based on time-separated recording and readout processes.

Joint transform correlator subtracting a modified Fourier spectrum.

The optically generated joint Fourier transform (JFT) of a test image and a reference image is processed using a new method: the JFT is recorded twice. In the second recording the reference image is phase shifted by π with respect to the first recording. The two JFT's are subtracted and binarized with a threshold of zero.