IR Reflective Sensor 1-4mm
The IR Reflective Sensor uses an infra-red LED and a phototransistor to measure the distance of an object between 1mm and 4mm away. This sensor can also detect the presence of an object up to 9mm away, but it won’t be able to reliably measure the distance.
This sensor works best with objects with smooth, opaque surfaces. Because of this, you can also use it to differentiate between a reflective object and a non-reflective object at the same distance.