When using line scan cameras, it is not necessary to illuminate the entire target. Therefore, images can be taken using a narrow area of the part. Illumination of the target can be classified in three ways.
Defective areas will appear as black since light does not return to the camera if there are flaws or dents.
Defective areas will appear as white by light applied to burrs and convex flaws reflecting towards the camera.
This is a method often used for measuring dimensions and for inspecting foreign objects on a sheet. Transmissive lighting will enhance the edges, and blockage of light will cause foreign objects to appear black when inspecting for foreign objects.