FOURIER-TRANSFORM SPECTROSCOPY USING LIQUID-CRYSTAL TECHNOLOGY

We report the use of a ferroelectric liquid-crystal (FLC) mask as an o ptical encoder for development of a solid-state Fourier-transform spec trometer. For this demonstration a 1 x 64 element array was striped an d used as a 1 x 4 element device. The device intersected dispersed rad iation and encoded each spectral component with a carrier signal by ap plying half-wave potential to each of the four striped (1 x 16) FLC el ements, which varied the transmitted amplitude of the light from 0.03% to 28% of full scale. The light was spectrally recombined and imaged onto a photomultiplier and the resulting carriers (and their amplitude s) detected by Fourier transformation of the time-varying signal. Spec tra of colored-glass filters were taken to demonstrate the possibiliti es of the instrument.