The virtual image still has the same angular height, however, which makes its apparent size appear infinitely large. The arrangement shown in Figure 5b illustrates a telephoto lens. A telephoto lens forms an image smaller than the real object, so telephoto lenses don't find much application in microscopes. You would use such a microscope when you need to examine a small object that you can't get close to. A telephoto lens forms the first optical element in such a microscope.
Subsequent lenses make up for the initial demagnification.
Long-distance microscopes find use on production lines that do not let manufacturers place microscopes close to the objects they must inspect. These objects include PCBs that must remain on a production tray or ink-jet cartridges that must remain in a jig. The object distance, which microscopists call the working distance , while quite short, is still longer than the lens' focal length. This type of lens arrangement can project a real image on a camera's detector placed in the focal plane. The camera can transmit to a display an image of magnified sample.