after testing with the IrSensor i realized I need a sensor with better range characteristics.

the Polaroid 6500 measures up to 10 Meters. It works just like a submarine sonar. It sends a ping and listens for the echo. the processor measures the delay and with some maths vs. the speed of sound the distance is known.

Picture shows the sensor mounted together with the camera in a turret on top of the Unimog cabin

this sensor comes with its own board and is connected to the MotherBoard

on this picture you can see the sensor mounted in the orange box together with the UnimogCam

see how I got a polaroid sensor from a used camera

some PDF documents I found describing the use of the Polaroid 6500:

• Polaroid Sonar Ranging Primer by acroname
• 6500 Series Sonar Raning Module technical data and circuits by Polaroid
• Sonar Manual by the University of Mississippi
• more pictures