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Optical Glass

Optical Glass

Date posted: October 6, 2017 // Optical Components

While the identity of its inventor remains in dispute, the first patent granted for a telescope was to a Dutch spectacle maker in 1608. As for the compound microscope, it seems to have appeared a little later in 1620 and, once again, although its inventor is uncertain, it appears that this may have been another Dutchman. Given the limited technology of the time, it is amazing just how much progress was made in the field of astronomy by the likes of Galileo and, by Malphigi and Hooke, in the study of human and microbial biology, despite lacking the high-quality of optical glass available to the makers of scientific instrument makers today.

Prior to this success in combining the effects of two or more lenses to achieve magnification, attempts to improve the observation of both distant and close objects were limited by the use of the handheld, single-lensed device still found in many homes and referred to as a magnifying glass. A more compact version known as a loupe is the constant companion of the jeweller and is used to appraise the quality of diamonds and other gemstones.

Along with these simple magnifiers, most households are likely to own a pair of binoculars, or maybe even something a bit less obtrusive, for use at the theatre or opera. If not, probably at least one member is dependent upon the use of spectacles or contact lenses. While in the case of the latter, plastic lenses are cheaper and generally just as effective in correcting one’s vision, there is no doubt that, for the best possible performance, optical glass is the better option.

One area in which the demand for quality lenses has declined is that of photography. Today, the much-simplified point-and-shoot digital cameras and, to an even greater extent, the ubiquitous mobile phones, have superseded the once mandatory SLR, with sales of the latter now largely restricted to the professionals.

Among the many applications of optics with which members of the public may be less familiar is spectroscopy in which light from a luminous object is passed through a prism and examined using a small telescope. The number, size, and position of dark absorption lines in the resulting spectrum may then be studied to identify the substances present in the source. Various modifications of this same principle, known as spectrophotometry or absorptiometry, employ specialised instruments to measure the concentration of specific substances present in a given sample – for example, the crucially important levels of the electrolytes sodium and potassium present in blood serum.

High-quality optical glass with a refractive index close to that of air is essential in the manufacture of the lenses and all other transparent components that may form part of the light path in instruments such as this. The high specification is necessary to ensure accurate wavelength selection and precision when measuring absorption.

A local leader in the supply of high-quality, vitreous materials and related equipment, LIT Africa offers a wide range of products relevant to this field. These include laser interferometers and 3D optical surface profilers from the US-based Zygo Corporation – global leaders in advanced optical metrology systems, as well as coating services, interference filters, and other specialised optical glass components.