What is different about the Sharp IR Sensor?
Comparison to a Normal IR Sensor
A normal IR sensor simple looks for if a object is boucing back the IR light. This means that you can only tell weather or not there is an object pressent. Most of the time this is fine. However there are times when you also need to know how far away that object is. This is where the Sharp IR sensor differs. The Sharp sensor has a special detector that not only determins if there is light, but it can also measure how far away an object is and return an analog value of the distance.
How it Works
The detector in the Sharp IR sensor is similar to the imaging sensor found in digital cameras. Since the detector and the IR LED have a fixed distance and orentation to eachother, the distance of a object will affect the angle at which the light bounces back. Now by looking at where the light hits the detector it is possible to calculate the angle or the light and then the distance of the object. This all happens on the sensor.