Sacharias Jansen (c. 1580 - c. 1638) was a Dutch spectacle-maker from Middelburg credited with inventing, or contributing advances towards the invention of the telescope. Jansen is sometimes credited for inventing the first truly compound microscope. However, the origin of the microscope - just like the origin of the telescope - is a matter of debate.
His name is often written as Zacharias Jansen or Zacharias Janssen, but as Dutch scientific literature writes the name as Sacharias Jansen, that way of writing it is also used in this article.
In 2008, the Netherlands commemorated the 400th anniversary of the telescope, honoring Jansen as one of the two possible inventors of the telescope, the other being Hans Lippershey.
In 1590 the Dutchmen Hans and Zacharias Janssen (Father and son) invented the first compound microscope. It would have a single glass lens of short focal length for the objective, and another single glass lens for the eyepiece or ocular. A resident of Delft, Anton van Leeuwenhoek, effectively launched high-power microscopy using single-lens, simple microscopes. With these modest instruments he discovered the world of micro-organisms. Modern microscopes are far more complex, with multiple lens components in both objective and eyepiece assemblies. These multi-component lenses are designed to reduce aberrations, particularly chromatic aberration and spherical aberration. In modern microscopes the mirror is replaced by a lamp unit providing stable, controllable illumination. However, today's optical microscopes evolved from these early Dutch designs.
