Resolution is a crucial issue in an imaging fiber bundle.
The figure here shows how an image is carried from one end of the bundle to the other. Each fiber core carries its own segment of the image to the other end, maintaining its alignment.
To visualize what happens, imagine that each fiber core captures a chunk of the image and delivers it to the other end of the bundle. This process averages out any details that fall within a single core. For example, if the input to a single core is half black and half white, the output will be gray. Thus, the fiber cores must be small to see much detail. For a stationary fiber bundle, the resolution is about half a line pair per fiber core, meaning two fiber core widths are needed to measure a line pair. Numerically, that means 10 pm fiber cores could resolve 50 line pairs per millimeter (1 line pair per 20 pm). Imaging bundles have fiber cores as small as 3 pm. Resolution is significantly higher— about 0.8 line pair per fiber core diameter— if the fiber bundle is moving with respect to the object.
Per fiber core diameter— if the fiber bundle is moving with respect to the object.
Before you wonder too much about the quality of fiber-bundle images, you should realize that fiber cores typically are about 10 pm. If that was the case, the letter A in Figure 30.3 would be only 60 pm high, less than 1/16 mm tall.
That’s many times smaller than the finest of fine prints used in legal documents. You have to look very hard, and may need a strong magnifying lens to see the individual fiber spots on a good imaging bundle.