What does a person consist of? Their organs? Their blood? How does life work? Finding the answer to many fundamental questions of humanity would not have been conceivable without the microscope. A technology that was revolutionised when it was put on a scientific foundation for the first time.
Jena, in the middle of the 19th Century. The city on the Saale, which Goethe once respectfully called the “City of Knowledge”, was, economically at least, dominated by its university and small craft businesses which lived on science-related orders. Far beyond the city limits of Jena, this was the start of a new era in natural sciences and medicine: Researchers began to understand the fundamental structure of living organisms, the meaning of the term "cell" became more and more developed. It was against this background that the 30-year-old Carl Zeiss (1816-1888) opened a workshop for precision mechanics and optics on 17 November 1846 at Neugasse No. 7 in Jena - a foundation stone and cradle of over 170 years of company history that has lasted to this very day.
Exploring the microcosm
The beginnings of microscopy go back to the middle of the 17th Century and its long history shows that it part of human nature to want to make the tiniest thing to the human eye - the microcosm - visible. But only the increasing importance and progress in scientific research and medicine at the beginning of the 19th Century made a device which once primarily served amusement, into an extremely important scientific instrument. And so, in the year 1847, on the advice of his academic teacher Matthias Jacob Schleiden (1804-1881), botanist and co-founder of the cell theory, Carl Zeiss began making simple but precise microscopes. Through his diligence, he quickly became a name, the need and demand for his products proved he had made the right decision. But only compound microscopes could achieve higher magnifications. For Zeiss to stay with the competition, he also had to build a compound microscope; in 1857 ”Stativ I” became the first technical milestone of his young company.
At the time, microscope lenses were developed experimentally through the tedious process of fiddling with combinations of achromatic lenses by trying out different lens combinations. Something which stood contrary to stable production and better optical properties. Recognising the need for putting the construction of microscopic optics onto a solid scientific foundation was one of Carl Zeiss’s fundamental achievements. His decision to work scientifically in the development of instruments has a milestone character and is still one of the basic principles of the company today. It led to a close and fruitful partnership with the physicist Ernst Carl Abbe (1840-1905), who, at the time, was a private lecturer at the University of Jena. Zeiss recruited him as a scientific employee in 1866 and then as a dormant partner in the business in 1876.
At Zeiss, Abbe began to focus on the calculation of optical systems at the end of the 1860’s. The results were ground-breaking and led to the basic understanding of microscopic image theories. Abbe's resolution limit means that the wave-like nature of light sets natural limits in the visibility of fine structures, which is less than half of the wavelength of the light. During his investigations, he found the formula for the (Abbe's) sine condition as a criterion for a sharp figure in the area of the optical axis and coined the term ‘numerical aperture’ (N.A.). Ultimately, he is responsible for the realisation that, under optimal conditions, when using violet light and a numerical aperture of 1.4, a resolution of approximately 0.2 µm can theoretically be achieved in a light microscope.
From 1872, microscopes at Zeiss were produced on the basis of scientific calculations - with much better optical properties. In 1877, the first homogeneous oil immersion object lens followed. It laid the basis for the oil immersion used in almost all laboratories today and - in addition to other benefits - led to a significant improvement in resolutions. Ernst Abbe was now able to calculate microscope lenses in such a way that some significant aberrations could be bypassed. Now, the quality of optical lenses limited the consistent use of its findings. So, it was helpful that the young chemist Otto Schott (1851-1935) had just melted a new type of glass that seemed ideal for optical purposes. Together, they opened a glass technical laboratory in Jena in 1882. His subsequent work permitted the production of glass with homogeneous, precisely determinable optical properties. The foundation was laid for apochromatic lenses - marketed as a completely new type of microscope object lens in 1886.
A pioneer for research
The basic understanding of optical theories not only gave Zeiss a significant advantage over its competitors as a company but also enabled ground-breaking work in the natural sciences and medicine. Robert Koch discovered the pathogens of tuberculosis and cholera in the 1880’s, for which he won the Nobel Prize for Medicine in 1905. In a letter to Carl Zeiss in 1904, he wrote: “But I owe a large part of the successes which I have been able to make in science to your excellent microscopes.” In the following year, 1906, Santiago Ramón Y Cajal, Spanish neuroscientist and histologist, together with Camillo Golgi, won the Nobel Prize for Physiology and Medicine for his fundamental work on the development and fine structure of the nervous system. Cajal had also used a microscope from Zeiss. Until today, more than 30 Nobel Prize winners have used Zeiss technology for their research.