The OPB608 is a reflective switch that consist of an infrared emitting device (LED or VCSEL) and an NPN silicon phototransistor mounted "side-by-side" on a parallel axis in a black opaque plastic housing. Both the emitting device and phototransistor are encapsulated in a visible filtering epoxy except the OPB608R. The phototransistor responds to radiation from the emitter only when a reflective object passes within its field of view. The phototransistor has enhanced low current roll off to improve the contrast ratio and immunity to background irradiance. The LED versions are designed for near field applications with the VCSEL version being designed for longer distances. The OPB608A/B/C devices are designed for applications with reflective distances between 0.050" and 0.375" and when the light pattern is not to be seen by the human eye except for the OPB608R. By utilizing the night enhancement function of a camera, the near infrared light pattern can be seen. This allows the user to see the pattern shining on the reflective object. The OPB608R device is designed for applications with reflective distances between 0.050" and 0.300" and when the light pattern is to be seen by the human eye. The efficiency of the sensor is lower for optical wavelengths in the visible range thus reducing the distance that can be used.