An active illumination three-dimensional sensor device is configured with a number of diagnostic functions that can satisfy the requirements of industrial safety within the context of a single-channel safety sensor architecture. The sensor diagnostic functions provide sufficient diagnostic coverage for an optical safety sensor (e.g., a time-of-flight safety sensor) to achieve a desired safety integrity level without the need for multiple channels. The diagnostic features can be applied to one or more components along the single-channel path (e.g., the sequencer, the illumination source, input and/or output optics, image sensor pixel, etc.) to provide a level of diagnostic coverage that renders the optical safety sensor suitable for use within industrial safety applications requiring high safety integrity levels.