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

The invention relates to a three-dimensional imaging system for calculating correlation flight time by means of sparse aperture compression. The three-dimensional imaging system comprises a pulse light source emission unit, an expanded beam lens, a fourth collimating lens, a random optical modulation unit, 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, a total-reflection mirror, a convergence light receiving lens, an optical 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.