A device having: an optical system configured to be controlled to adjust a focal position so as to focus in an adjustment range; a switch configured to be switched between a first state and a second state; and a processor comprising hardware, wherein the processor is configured to implement: a focal position adjustment range setting unit configured to set: the adjustment range to a whole region in the first state; and the adjustment range to a part of the whole region in the second state, wherein the part of the whole region as a predetermined range is determined from a focal position of an object point conjugate with an imaging surface at the time the first switch is switched to the second state; and a controller configured to control the optical system to adjust the focal position based on the set adjustment range.