Device for monitoring a shaft coupling coupling a first shaft to a second shaft

A dynamoelectric rotary machine, comprising:

• a first shaft;
• a second shaft;
• a shaft coupling designed to couple the first shaft and the second shaft;
• and
• a device for monitoring the shaft coupling, said device comprising an optical unit comprising a receiving element designed to receive an electromagnetic radiation, and a modifying unit designed to modify a radiant energy impinging on the receiving element as the first shaft runs asynchronously with respect to the second shaft, said modifying unit comprising a holographic optical component designed for arrangement on and/or within the first shaft, and a diaphragm designed for arrangement on and/or within the second shaft and comprising radially arranged slots and radially arranged filled regions in an at least substantially regular sequence, said diaphragm comprising an at least substantially centrally arranged opening, wherein the holographic optical component is designed for illumination or irradiation with the electromagnetic radiation and generates a pattern having radially arranged areas with a first radiant energy and radially arranged areas with a second radiant energy in an at least substantially regular sequence.