Depending on the size of the conductor board, between eight and 20 measuring positions can be realized. During movement, the sensor is exposed to very high accelerations, which places special demands on the mechanical resistance. The mechanical solidity of the sensor is attained by using a construction consisting of carbon, on which the sensor components were bolt and glued.
The surface of a conductor board to be analyzed is very inhomogeneous. The soldering paste, which is only applied to metallic surfaces, reflects the projecting light mostly diffusely, which is pre-condition for a specific sensor measurement accuracy. By contrast, the conductor board substrate has mostly both reflecting and translucent surfaces. This leads to systematic and random measurement errors. These errors are eliminated by choosing an angle of incidence of the projecting light such that the occurring reflection will no longer be projected on the camera images. The systematic error, which appears because of the penetration of the projecting light into the conductor board surface, is compensated by correction values which are determined experimentally. Figure 2 shows a conductor board and the measurement result. In contrast to previously developed systems, strict reduction of the picture recording time and accelerated computing had to be reached in order to achieve the requested testing velocity. This was realized by implementation of a series of new algorithms. The phase determination algorithm was expanded for any phase steps. The eight- and the six-phase algorithm, respectively, are used in the system.