I hope this is the correct place to ask this. If not, please refer me to a better place, thanks. Now to my question,

I am learning about digital image processing, and the book I am reading is discussing spatial resolution. They discuss spatial resolution in terms of line pairs. They talk about constructing a chart with pairs of dark and light lines, and how the width of a line pair is the width of a light and dark line. This is all of the information the book gives about line pairs, and I don't really understand what role these play in digital image formation and resolution.

What does a line pair actually correspond to or respresent in the context of image formation, specifically in a camera? There is a question in my book about how many line pairs/mm a camera will be able to resolve when taking an image of a subject. It gives the size of the CCD in the camera, as well as how many elements there are vertically and horizontally in the CCD. What does line pairs/mm of the CCD mean? Is this something like the number of pixels that will be resolved per CCD element? It just isn't clear to me how line pairs are realized in the camera.

I hope this question makes sense. I am a CS student so don't do much of anything with signal processing, but I would like to have a better understanding of how images are formed with respect to their spatial resolution capabilities.