1. An image acquisition apparatus comprising: an imaging device on which an image of a small area allocated to an area to be imaged is formed; a detection section detecting intensity of light irradiated on the small area from a light source; an integration section integrating the intensity of light detected by the detection section; if an integration value of the intensity of light integrated by the integration section from a point in time when light is emitted from the light source is greater than a predetermined threshold value, a light-source control section terminates emission of light from the light source; an exposure control section starting exposure of the imaging device before light is emitted from the light source and terminating exposure of the imaging device after emission of light from the light source is terminated; and an image acquisition section acquiring the image of the small area as a divided image from the imaging device.