Laser phase shift distance meter for vision based driver assistance systems

Camera based systems are gaining popularity in automotive driver assistance systems. They are used to detect obstacles, road signs, road markings and other road users. Today, even low cost camera technology enables obtaining a very good image resolution and therefore cameras are able to give a good 2-dimensional image. Due to the projection of an image into the camera´s sensor plane, its main disadvantage is the difficulty to estimate the distance of objects projected onto the sensor plane. This difficulty can be overcome if image information is exchanged by several cars via car-to-car-communication. Thinkable solutions range from simply exchanging estimated positions of detected objects up to tomographic image processing. For these methods, knowledge of an exact position of the vehicles is crucial. Conventional positioning methods do not deliver the required accuracy. Therefore a phase shift laser distance measuring device is proposed that is used to measure the vehicles precise position relative to landmarks. Considering the special requirements resulting from this application, the new laser measurement system design is introduced. Measurement results demonstrate its applicability. Special attention is laid on error sources such as crosstalk in this new implementation of a phase shift laser range finder.