Carl Kellner was a German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 mechanic and self-educated

Autodidacticism

Autodidacticism is self-education or self-directed learning. In a sense, autodidacticism is "learning on your own" or "by yourself", and an autodidact is a person who teaches him or herself something. The term has its roots in the Ancient Greek words αὐτός and διδακτικός...

 mathematician

Mathematician

A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

 who founded in 1849 an "Optical Institute" that later became the Leitz company, makers of the Leica cameras.

Biography

Carl Kellner was born in Hirzenhain

Hirzenhain

Hirzenhain is a municipality in the Wetteraukreis, in Hesse, Germany. It is located approx. 45 kilometers northeast of Frankfurt am Main....

, Wetteraukreis

Wetteraukreis

The Wetteraukreis is a Kreis in the middle of Hesse, Germany. Neighbouring districts are Landkreis Gießen, Vogelsbergkreis, Main-Kinzig-Kreis, district-free Stadt Frankfurt, Hochtaunuskreis, Lahn-Dill-Kreis.-History:...

, in Hesse

Hesse

Hesse or Hessia is both a cultural region of Germany and the name of an individual German state.* The cultural region of Hesse includes both the State of Hesse and the area known as Rhenish Hesse in the neighbouring Rhineland-Palatinate state...

. In 1849 he founded in Wetzlar

Wetzlar

Wetzlar is a city in the state of Hesse, Germany. Located at 8° 30′ E, 50° 34′ N, Wetzlar straddles the river Lahn and is on the German Timber-Framework Road which passes mile upon mile of half-timbered houses. Historically, the city has acted as the hub of the Lahn-Dill-Kreis on the north edge of...

 a company called "Optisches Institut" for the production of lenses

Lens (optics)

A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...

 and microscope

Microscope

A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

s. Kellner had invented a new achromatic

Achromatic lens

An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths into focus in the same plane....

 combination of lenses for an eyepiece

Eyepiece

An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings...

, published in his treatise Das orthoskopische Ocular, eine neu erfundene achromatische Linsencombination, that was able to produce an image with correct perspective

Perspective (visual)

Perspective, in context of vision and visual perception, is the way in which objects appear to the eye based on their spatial attributes; or their dimensions and the position of the eye relative to the objects...

 and without the distortions that were usual for other optical instruments of the time. His invention is still useful and known as the Kellner eyepiece.

Legacy

After his early death in Wetzlar, his widow led the company, which had twelve employees at that time. In 1856, she married her employee Friedrich Belthle (February 27, 1829 – May 9, 1869), who from then on managed the company. In 1864, precision mechanic Ernst Leitz joined them; he became a partner on October 7, 1865, took over the company in 1869 and re-founded it as the Ernst Leitz GmbH. The company expanded quickly; its newly developed binocular

Binocular vision

Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...

microscope was a market success.