There are tw
o basic configurations of the conventional optical microscope: the simple microscope and the compound microscope. The vast majority of modern research microscopes are compound microscopes while some cheaper commercial digital microscopes are simple single lens microscopes. static; to focus at different focal depths the lens to sample distance is adjusted, and to get a wider or narrower field of view a different magnification objective lens must be used. Most modern research microscopes also have a separate set of optics for illuminating the sample.