1. An image acquisition device, comprising: a stage on which a sample is placed; a light source configured to emit instantaneous light; a light guiding optical system including an objective lens arranged to face the sample on the stage; an imaging sensor configured to capture an optical image of the sample guided by the light guiding optical system; a driver configured to move a position of a field of view of the objective lens relative to the sample at a predetermined velocity; and a controller configured to control the light source, wherein the imaging sensor is a two-dimensional imaging sensor including a plurality of pixel rows and for sequentially capturing at a predetermined frame rate, and the velocity is a velocity set by the following formula: 
 V′=A ×( M−N )×α, where A denotes pixel resolution, M denotes the number of pixel rows of the imaging sensor, N denotes the number of pixel rows of the imaging sensor corresponding to an overlapping region in which portions of two regions of the sample to be continuously captured by the imaging sensor overlap each other, and α denotes the frame rate.