Optical sensors belong to the group of non-contact measuring, geometry-oriented
sensors (Figure 1). For information retrieval, the weld groove is scanned via a radiation detector which records the emitted optical radiation of the measured object. Semiconductor image sensors are applied for the detection of radiation. The optical measuring principles are differentiated into sensors with and without active structured lighting. If there is no active structured lighting, a camera is used for signal acquisition. The camera observes the workpiece and extracts the required information from the two-dimensional halftone picture. Active structured lighting means the application of a light source for the defined lighting of specified regions of the part. For the subsequent acquisition, single photo elements, lines or arrays can be used, depending on their design.