A typical field of application for line scan cameras is the inspection of a continuous product such as a textile, paper, glass or steel plate. These objects have no defined beginning or end and can be thought of as infinite in length.
Imaging objects on a conveyor belt is also an excellent use for line scan technology, especially if the objects under inspection vary in length and a high resolution image is required. Capturing images with an area scan camera would require a vertical field of view large enough for the biggest part, limiting the resolution. In addition, illuminating large areas can be a problem. Line scan gets round these problems by effectively varying the image height depending on start/stop signals derived from the part as it moves past the camera. In addition it is far easier to illuminate a single line across the conveyor.
Line scan is also a very convenient way of imaging cylindrical components. Trying to do this with an area scan camera would be difficult and would involve correcting the distortion caused by imaging the curved surface, plus having to take multiple images to capture the entire surface. A line scan camera records the same optical position across the whole cylinder eliminating distortion; rotating the cylinder will generate an "unwrapped" image of the entire surface.