How to Build a Circuit to Detect a Black Line?

[rusty009]

Hey, I need to build a circuit that needs to detect a black line. And I need some help, if someone could please tell me what components I should look into rather than already designed circuits that would be a huge help ! Thanks in advance.

 

[dlgoff]

An optical sensor comes to mind. Maybe a photodiode or phototransistor.
Here's a discussion that may provide some help: https://www.physicsforums.com/showthread.php?t=249457&highlight=line+detect

 

[Pumblechook]

I think people would get a better response if they explained a bit more.

Black line where? How thick? How long? Against what backgound? Straight? For exactly what purpose?