The onboard GP2S700HCP photointerrupter puts this click board in a reflective mood.
IR reflect click is a cousin to the previously released IR eclipse click. The latter has a photointerrupter in which the transmitter and receiver face each other; on IR reflect, the pair faces the same direction.
On IR eclipse the sensor is triggered when the infrared beam is obstructed, IR reflect works the opposite way: when the infrared beam bounces back from an object placed near the sensor, the receiver catches it. IR eclipse click is like a tennis match between receiver and transmitter, IR reflect is like a game of squash.
The phototransistor outputs the signal through the mikroBUS™ AN pin. You can also set a threshold for triggering an interrupt, using the onboard potentiometer.
The optimal detecting range of IR reflect click is 3mm. You'll get different results depending on the object you place in its vicinity. Shiny metallic surfaces readily reflect the infrared beam from a greater distance than anything else, while black objects won't trigger it at all.
Also, other infrared light sources (which can come from an ordinary incandescent light bulb) can negatively impact the performance of the sensor.