A process is provided for the hemihydrogenation of dinitriles to corresponding aminonitriles using hydrogen in the presence of a supported catalyst. A pair of light sources have horizontal light axes which are orthogonally related and intersect the container axis. These intermediate images are saved to a PACS or other memory storage, and can be recalled later to reconstruct an image. Cavities are provided at the ends of auxiliary waveguides connected to the directional couplers, and monitor light is guideded into these cavities.