The first microscopes had only one lens and were not much more than a magnifying glass. Soon after, however, lens systems were devised that were to supply a larger magnification and a clear image. Microscopes with more than one lens are also called compound microscopes. This compound microscope consists of a tube with at the end an objective lens (the objective) and at the other end an eye lens (the ocular). The objective generates a magnified image of the object. The ocular serves as a magnifying glass with respect to this image. The microscope has a magnifying factor up to 200 times. In later developments of the microscope, the objective no longer consisted of one lens, but of a complete lens system. The ocular too was soon extended: in order to broaden the field of vision, a so-called field lens was placed before it, after an idea of Christiaan Huygens from 1656.