Catadioptric Sensor for Microassembly using Mirror Prisms

Metrology for Production

Hybrid micro systems are preferably assembled serially by robots, which the components successivly in their intended positions. Acceptable quality and ecomonical yield can often only be achieved, if deviations arising are immediately detected and corrective actions are taken before completion of an assembly step. Photogrammetric sensors using electronic cameras are especially well suited for this purpose, as they can measure the the spatial position and orientation of microcomponents withoout infering with small and lightweight microparts.

The planned thesis will present an sterophotogrammetric sensor for direct integration into robots for microassembly. The sensor employs an optical module incorporating two prisms. The lateral faces of the prism are covered with reflective coating and form a beam-splitting mirror optics (catadioptric system). The mirrors permit a single electronic camera to record two image of assembly process from two different spatial direction. This stereophotogrammetric setup has a very compact size, as the prisms have small size, and the camera can be placed directly above the measuring volume. The optical module replaces a considerable number of optomechanical components, increasing the reliability of the sensor.

The light coming the measured object has to pass the prisms before it enters the camera. The refraction at the interfaces between air and glass lead to additional distortions, which have be considered during measurements. The refraction may also deteriorate the optical performance of the camera lens. Special care has to taken of unwanted total internal reflection on the entry and exit faces of the prisms.

TU Braunschweig
in progress
Ph.D. student: