Low coherence light having a central
wavelength λc of 1.1 μm and a
full width at half maximum spectrum Δλ of 90 nm is emitted. The low coherence light has
wavelength properties suited for the light absorbing properties, the
diffusion properties, and the dispersion properties of living tissue. A light dividing means divides the low coherence light into a measuring
light beam, which is irradiated onto a measurement target via an optical probe, and a reference
light beam that propagates toward an
optical path length adjusting means. A
multiplexing means multiplexes a reflected
light beam, which is the measuring light beam reflected at a predetermined depth of the measurement target, and the reference light beam, to form coherent light. A coherent light detecting means detects the
optical intensity of the multiplexed coherent light. An image obtaining means performs image processes, and displays an optical
tomographic image on a display apparatus.