TEMPORALLY MULTIPLEXED FOURIER HOLOGRAPHY AND PATTERN-RECOGNITION OF FEMTOSECOND-DURATION IMAGES

Image frames of femtosecond duration have been recorded and successive ly played back by (1+2)-dimensional Fourier holograms in a spectral ho le 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 repres entation) into modulation of dye density over the hologram plate. It i s shown that separately recorded frames are recalled successively by t he re ad-out pulse. Streak-camera measurements on model signals ascert ain that despite the circumstance that molecules of the same absorptio n frequency and spatial location carry simultaneously information abou t the different frames recorded, there is no crosstalk between the fra mes, i.e. they are distinctly separated in time in accordance with val ues of delays set relative to the reference pulse in the recording pro cedure. A possibility to perform pattern recognition by a single holog ram plate containing two 2-D filters matched to different text fragmen ts on a microfilm slide, is demonstrated.