A microprocessor is operably coupled to a camera from which patient vital signs are determined. A temporal-variation-amplifier of at least two images is operable to generate a temporal variation, a vital-sign generator is operable to generate at least one vital sign from the temporal variation and a display device is operable to display the at least one vital sign.

A display apparatus includes a detector configured to detect an infrared ray emitted from a human body; a state signal generator configured to generate a state signal including at least one of a first state signal component indicating that the human body is approaching the detector and a second state signal component indicating that the human body is leaving from the detector in response to an intensity variance of the infrared ray detected with the detector; and a controller configured to start controlling an external device upon detecting the first state signal component from the state signal generated by the state signal generator but to stop controlling the external device upon detecting the second state signal component from the state signal.