Sharp Infrared Proximity Sensor is a product of Sharp Corporation. It measures the distance of an object that is between 10cm and 80cm away. The IR sensor works by sending an infrared signal through its transmitter. If there is an object within range, this signal is reflected. On the other hand, the receiver on the sensor detects the reflected IR signal and generates a corresponding analog output voltage. You can map this voltage to distance using the ADC.
Check out this Sharp Infrared Proximity Sensor Project