1. A method for monitoring the interior space of a motor vehicle by means of IR radiation, comprising the acts of: placing at least one stationary IR transmitter and at least one stationary IR receiver for receiving reflected IR radiation in a central position in the vehicle interior space, wherein the stationary IR receiver is an IR camera; temporarily irradiating the vehicle interior space; recording two images of the interior space at different illumination levels; and subtracting the two images from one another with respect to their gray scale values for suppression of interfering effects.