PROBLEM TO BE SOLVED: To provide an OCT system for forming tomographic imageS by means of Fourier transformation, using a single photodetector unit.SOLUTION: The rear stage of the interferometer constituting the OCT system is provided with a light pulse time sharing multiplication unit which delays a second binding light pulse (interference light pulse) by a predetermined delay time behind a first binding light pulse (inference light pulse), and subsequently allowing the first binding light pulse to merge with the second binding light pulse to alternately emit the first binding light pulse and the second binding light pulse.