What this sensor is and what it brings to a panel
The Omron E3FA-VP21 is an M18 threaded cylindrical photoelectric sensor using diffuse-reflective sensing with a limited 50 mm range. It runs on 10 to 30 VDC and switches a PNP output, selectable for light-on or dark-on operation via a wire connection. The M18 body and M12 4-pin connector are standard industrial sizes, so this sensor fits common brackets and pre-made cables without adapters.
The E3FA-BP22 is the same M18 barrel, same M12 connector, same PNP output, and same L-ON/D-ON selectability, but it uses retro-reflective sensing and reaches 2 meters instead of 50 mm. Mechanically and electrically, the two sensors are a direct swap — same wiring, same mounting, same pinout. The decision comes down to whether your target calls for diffuse (object reflects light) or retro-reflective (reflector required). If the existing panel was built for the E3FA-BP22, this unit will bolt in and wire up, but the sensing method change may require re-evaluating the application.