Line sensor

The line sensors detect the presence of a black line by emitting infrared light and detecting the light levels that return to the sensor. The device will emit IR light and the sensor will capture the light level that is reflected from the surface underneath it.
This sensor works by detecting reflected light coming from its infrared LED. The amount of reflected infrared light can detect transitions from light to dark lines.

 The line sensors with a large measuring range

This sensor is used for sensing white lines on a dark surface and black lines on light surfaces. 0.18 volt on the bright surface and 2.2 volts on the dark surface. Output is analog. In the analog output, one can write a complex algorithm to follow the white line using a micro controller.