Two proximity sensors in android phone

Question

In my android phone with two proximity sensors and I can easily log the front proximity sensor value.

   if(event.sensor.getType() == Sensor.TYPE_PROXIMITY){
           Log.d("PROXIMITY",""+event.values[0]); }

However, I have no idea to get rear proximity sensor value. I have already search on developer.android.com without any success. I hope someone should have experience to grep value of rear proximity sensor.