The QTR-HD-01RC reflectance sensor part of Pololu is an integrated, high-power surface-mount device with an integrated LED light source and an integrated optical detector. It features a high resolution, 1.8° wide viewing angle, and an adjustable gain setting. The LED emits light in the visible red spectrum, which is reflected off of objects and detected by the photoreceptor, providing a variable analog output that is proportional to the amount of reflection. This makes the QTR-HD-01RC ideal for color and line detection, as well as general-purpose reflection sensing and daylight sensing applications. Additionally, the output signal is designed to be unaffected by the hue or intensity of the ambient light, allowing for accurate readings regardless of the lighting conditions.