Abstract: An ultrasonic sensor for performing sensing a spatial area and/or measuring ontactless a distance has at least one ultrasonic transducer for sending ultrasonic impulses and/or receiving the echo of the ultrasonic impulses. A device for concentrating the energy of the ultrasonic impulses onto a spatial area to be sensed and for concentrating the energy of the echo of the ultrasonic impulses onto the at least one ultrasonic transducer is provided. The device for concentrating the energy has a reflector with a reflective surface. The reflective surface has parabolic surfaces of second order. The reflector comprises reflector segments that are rigidly or movably connected to one another. A first and second reflector segments are outer segments having reflective surfaces that are paraboloid segments of 50.degree. to 120.degree. of a paraboloid of revolution with a first focal point.