During the development of a low cost industrial optical sensor an unexpected drift phenomenon has shown to be critical to performance. The sensor is based on LED's as light sources and the main source of error could be tracked to the instability of the spatial radiation pattern of the LED's. This instability due to the construction of the sensor introduced an error in the intensity feedback loop. Alternative designs including a Y-coupler, a scattering arrangement and a mirror beam splitter have been investigated and the results are presented.
