Reflective sensing, active line
The Omron EE-SY190 is a reflective-type miniature photoelectric switch — the emitter and receiver sit in the same housing, and the sensor detects the target by the light reflected back. This is the configuration to confirm when replacing a thru-beam unit, because the wiring and mounting footprint differ. Listed as current production, so the part is still in the active Omron catalogue and available through the franchise channel.