1. A method of obtaining an AO (Adaptive Optics) image of an area of a subject, the method comprising: providing light from a light source; a fast scanning step of scanning the light in a first direction by a first scanner to produce a first scanning line of light; a slow scanning step of scanning the first scanning line of light in a second direction by a second scanner, wherein the second direction is substantially orthogonal to the first direction to produce a first scanning area, wherein a scanning rate of the slow scanning step is lower than a scanning rate of the fast scanning step; an image constructing step of constructing an image with light from the first scanning area of the subject; a position detecting step of detecting a relative change in a position of the first scanning area on the subject by analyzing the image constructed in the image constructing step; a tracking step of tracking the first scanning area by controlling the second scanner according to the detected relative change in the position of the first scanning area; and an AO image constructing step of constructing the AO image by adjusting a position of the image using the detected relative change in the position of the first scanning area.