Temporally multiplexed Fourier holography and pattern recognition of femtosecond-duration images

Abstract Image frames of femtosecond duration have been recorded and successively played back by (1 + 2)-dimensional Fourier holograms in a spectral hole burning medium. The duration and timing of frames are encoded into modulation of the distribution of dye molecules over their absorption frequencies, while images are encoded (in 2-D spatial-frequency representation) into modulation of dye density over the hologram plate. It is shown that separately recorded frames are recalled successively by the read-out pulse. Streak-camera measurements on model signals ascertain that despite the circumstance that molecules of the same absorption frequency and spatial location carry simultaneously information about the different frames recorded, there is no crosstalk between the frames, i.e. they are distinctly separated in time in accordance with values of delays set relative to the reference pulse in the recording procedure. A possibility to perform pattern recognition by a single hologram plate containing two 2-D filters matched to different text fragments on a microfilm slide, is demonstrated.