VISHAY SEMICONDUCTORCNY70 OPTICAL SENSOR (SWITCH) REFLECTIVE (5 pieces)

The best thing about this sensor is that it has a printed datasheet and very detailed parameters. This worked well with the comparator I was using in my project. The datasheet suggests 3mm is optimum but I was able to get it to switch on and off at 2 ft. Realize there is no resolution that far but it is sensitive enough to see a large white object that far.