The Pololu QTR-MD-01RC Reflectance Sensor is a long-range, digital optical sensor that provides a versatile and easy-to-use method to measure surface reflectance from up to 16 cm away. This makes it ideal for detecting a wide variety of objects, from clothing and paper to black wafers, plastic pieces, and more. Its gray scale detection capability allows for further categories of objects to be accurately identified. The sensing range and measurement accuracy can be tuned to meet the needs of a given application. It features two emitter LEDs with selectable wavelengths of 880 nm and 940 nm, and four detector channels that produce analog signals proportional to the reflectance of the surface under the sensor.