The dispersion characteristics of optical coherence tomography (OCT) system were particularly analyzed. It is found that the dispersion is proportion to the defocus distance of a galvanometer

with negative in the focus length

dispersion

and with possive dispersion out the focus length. A OCT with spatial resolution of 8 μm is designed. The dispersion of 77 fs

2

is measured in this OCT system when the galvanometer is 0.5 mm far away from the focal length of Fourier lens. The relation between dispersion and the distance away from focus is experimentally validated

and the experimental results are agreed with theory well.