On our historical pages we trace developments right back to their early days. And you will also learn more about the leading rights who discovered them.
Carl Zeiss opened an opto-mechanical workshop in 1846 and enjoyed an excellent reputation as a manufacturer of microscopes. Although close co-operation with renowned scientists ensured that Carl Zeiss constantly improved the quality of microscopes, it was not until his collaboration with Ernst Abbe (from 1866) that he was able to place the building of microscopes on a sound scientific foundation. To be able to produce glass on the basis of Abbe’s latest scientific discoveries, Otto Schott, Ernst Abbe, Carl Zeiss and Roderich Zeiss founded the "Glastechnisches Laboratorium Schott und Genossen" (now the company Schott Glas) in 1883.
Until this time, optical glass had only been differentiated by the specification of its "specific weight"! Abbe introduced a further important parameter for the first time – a parameter without which present-day ophthalmic optics would be difficult to imagine: the ratio of refraction to dispersion – the Abbe number and was later used for the production of plastic lenses.
At the turn of the century Josef von Fraunhofer (1787 – 1826) observed that old lenses with weathered surfaces displayed higher transmission. Changes caused by corrosion reduced the refractive index in the upper layers of glass. This resulted in decreased reflection and therefore increased transmission.
The English optician Denis Taylor went one step further by deliberately using acid to artificially corrode lenses. Although this method was patented in 1904, it remained more or less insignificant, as the treatment made the surfaces of the lenses porous and hence considerably less durable.
In 1935, A. Smakula in the company Carl Zeiss found a new method of reducing reflections on optical surfaces. He succeeded in applying an additional coating to the surface of a lens which not only caused a reduction in reflections, but also displayed good durability at the same time. The patent for this method was kept secret until 1939; it was not until a similar method was successfully developed in the USA that the patent was finally released.
To this very day, Smakula’s work forms the basis of the standard procedures used to reduce reflections on spectacle lenses.
In ca. 1804 the English physician Wollaston discovered that visual acuity decreases when a spectacle wearer looks through the periphery of the biconvex lenses used at that time, and that meniscus-shaped lenses provided a sharper image. After this discovery, repeated attempts were made to improve the imaging properties of lenses. The first endeavours to design meniscus-shaped lenses with reduced peripheral blurring were undertaken by the ophthalmologists Ostwald and Tscherning. However, the results were of no practical significance, as they were only computed for very small viewing angles and for lenses with a theoretical centre thickness of zero.
In 1908 the company Carl Zeiss entrusted a member of its scientific staff, Moritz von Rohr, with the exact computation of spectacle lenses. He succeeded in designing a point focal lens in which peripheral blurring was minimised. These computations of Moritz von Rohr laid the foundations for today’s Punktal lenses from ZEISS.
Although optimum imaging properties were achieved with the first point focal lenses, the pronounced curvature of the lenses proved to be a major cosmetic drawback, especially for high prescriptions in the plus range.
To make lenses more attractive, so-called periscopic lenses were introduced, in which one surface was almost flat. This also made the lens flatter overall, but considerable aberrations were experienced in the peripheral zones. In higher dioptric powers in particular, these aberrations led to blurred vision.
The solution – a good appearance and good vision with one and the same lens – came in the form of the asphere and the atorus.
In 1986 Carl Zeiss was the first manufacturer – and still is the only manufacturer – to offer a single vision lens with an atoroidal front surface: the Hypal lens. This modern surface design permits outstanding image quality over a wide field of view and, at the same time, flat, cosmetically attractive lenses.
Aspheric surface design is nothing new at ZEISS. Katral aspheric cataract lenses were launched on the market as long ago as 1923. However, the complex manufacturing technique required was reflected in a very high price: one Katral lens cost as much as a month’s rent for a 4-room luxury apartment in a prime city location at the time in question. It stands to reason that such a high price could not be asked for standard spectacle lenses on the market.
Mineral sheet glass was successfully produced as long ago as the 12th century. Church windows, for example, were made of small pieces of coloured glass held together by lead. However, only the Venetians mastered the art of producing totally clear glass at this time.
In Germany during this period, beryl (semiprecious gem) was still being used to magnify print when reading. The magnifying effect of these water-white, ground rock crystals was utilized by simply placing them directly on top of the text to be read.
The plastic CR 39 (Columbia Resin) was developed to produce organic spectacle lenses for the first time about 50 years ago.
Not only contraction of the pupils, but also closing of the eyelids protect the eyes against glare and UV radiation. This realisation probably led to what is known as "slit spectacles".
These wooden spectacles worn by Eskimos are one of the earliest forms of sun protection. Their narrow slits allow vision with little glare in regions where snow and ice reflect up to 80% of light.
Multifocal lenses and spectacles have existed in various forms for over 200 years now. The invention of bifocal lenses is attributable to the North American statesman Benjamin Franklin (Franklin lens). In 1785 he presented a pair of bifocal spectacles in which two half lenses were mounted on each side of the frame. The top lens was used for distance vision, and the bottom one for reading.
The term "bifocal" was coined by the mechanic John Isaac Hawkins who proposed a construction for trifocal spectacles as long ago as 1826.