Four-dimensional spectral imaging system and method for calculating correlation flight time by means of sparse aperture compression

The invention relates to a four-dimensional spectral imaging system for calculating correlation flight time by means of sparse aperture compression. The four-dimensional spectral imaging system comprises a pulse light source emission unit, an expanded beam lens, a fourth collimating lens, a random optical modulation unit, a total-reflection mirror, a polarized light beam splitter, a first lens, a beam spot synthesis unit, a sparse aperture unit, a free space collimation unit, a beam reflection unit, an expanded beam collimation unit, a spectral beam split unit, a convergence light receiving lens, a linear array detector, a flight time correlation unit and a compression calculation correlation algorithm module. The sparse aperture unit comprises at least three secondary telescope lenses, the free space collimation unit comprises at least three collimating lenses, and the beam reflection unit comprises at least three reflection mirror groups; one secondary telescope lens, one collimation lens and one reflection mirror form a light path; the flight time correlation unit comprises a pulse width regulation unit, an adjustable delay unit and a synchronous signal source.