Some embodiments are directed to a patient monitoring system for monitoring the location of a patient at a distance, including a projector operable to project a pattern of light onto the surface of a patient and a imaging system operable to obtain images of a patient on to whom a pattern of light is projected. A heat sink is associated with the projector. A heat source, such as an array of resistors, is configured to apply heat to the heat sink when the projector is not being operated, reducing variation in the temperature of the heat sink which in turn reduces variation in thermal expansion and contraction of the monitoring system which can be a potential source of error for determining the position of a patient being monitored.
