A display device is used in combination with a light-emitting device that emits first signal light. The display device has: a user interface unit that receives input operations using an indicator upon a display screen; and an imaging unit that captures images of the display screen and the first signal light. On the basis of captured images supplied from the imaging unit, the user interface unit takes a region of the display screen that is within a distance range that is determined in advance from the detected position of the first signal light as a valid operation region in which input operations using the indicator are valid.