Infrared sensors work by emitting bands or rays of light to determine whether or not there is a certain type of light wavelength in the nearby infrared spectrum. Infrared sensors essentially operate by using LED lights, which emit light of the same wavelength as light rays produced by the ideal IR spectrum.
With the emission of IR lights, infrared sensors are able to obtain information about the intensity, frequency and length of other light waves in the surrounding space. As objects become closer, light emitted from IR sensors bounces in greater intensity and frequency off of the surrounding objects. This action allows those objects to be detected by the light sensor, appearing as magnified images in the beam of light emitted from the IR sensor. In the absence of surrounding objects, the light sensors within infrared sensors do not detect any surrounding infrared light and, therefore, do not emit a characteristic red glow. In addition to determining the presence of infrared light, sensors may pick up reflected light and determine how bright a nearby object is. Typically, objects that are lighter in color reflect more infrared light, while those that are darker absorb infrared light beneath their surfaces.