The Pololu QTR-4052 is an analog infrared (IR) reflectance sensor array that is used for a variety of applications, such as line or edge following, obstacle detection, and proximity sensing. The unit consists of four IR reflectance sensors and one LED for each sensor, all housed in a single package. The sensors can measure distance (in the range of 5 to 100 mm) when powered by 3 - 5.5 VDC using an analog output. Each sensor can detect up to a 15° angle, allowing it to help sense objects in a relatively small area. The QTR-4052 is well suited for autonomous mobile robots and line-following robots.