Image-forming optical system

In optics an image-forming optical system is a system capable of being used for imaging.

The two traditional sytems are mirror-systems (catoptrics) and lens-systems (dioptrics), although in the late twentieth century, optical fiber was introduced.

Isaac Newton is reported to have designed what he called a "catadioptrical phantasmagoria", which can be interpreted to mean an elaborate structure of both mirrors and lenses.

Catoptrics and dioptrics have a focal point, whilst optical fiber transfers an image from one plane to another without an optical focus.

Catoptrics and optical fiber have no chromatic aberration, whilst dioptrics need to have this error corrected. Isaac Newton believed that such correction was impossible, because he thought the path of the light depended only on its color.

In 1757 John Dollond was able to create an achromatised dioptric, which was the forerunner of the lenses used in all popular photographic equipment today.