Sensor for monitoring the area near to a motor vehicle

The sensor has a lens (2) arranged behind a motor vehicle having an infrared emitter (3) and a receiver mechanism (4) for reflected infrared rays. A computer (5) receives a signal and passes it to a controller (19) in the motor vehicle. The infrared emitter (6) and receiver are intended for the measurement of a transparency of the lens (2). Reduced transparency is determined by the computer and indicates a higher signal from the infrared emitter (3) for the monitoring of close range. The infrared emitter provides a higher signal of up to 40 per cent over normal operation. The infrared emitter is intended for several measurements of the transparency of the lens. The receiver receives several transparency rays of the lens.