Patent US 5,483,335

Analysis of energy emanating from a source having a focal plane by converting the energy from the source into modulated spectral components simultaneously distributed according to frequency along a flat field, using, for example, a modulator, and then detecting and demodulating the spectral components, for example by a fast Fourier transform or synchronous demodulator with a ruled grating interposable between the source and the detector and a linear variable bandpass filter interposable between the source and the detector.