An image detection device includes a liquid resonant lens system whose focal point is cyclically changeable; an image detector configured to detect a detection image in a to-be-imaged region through the lens system; a pulsed illuminator configured to emit pulsed light on the to-be-imaged region in synchronization with the focal point; and an illumination controller configured to increase or decrease an illumination duration of the pulsed illuminator depending on a required light volume of the to-be-imaged region at the focal point where the pulsed illuminator emits pulsed light.