Turning The Lens On The Achromatic Lens

Photo credit : www.edmundoptics.com & www.micro.magnet.fsu.edu
Memory tags: A lentil shaped piece of glass that magnifies the unseen-associated with the scientist and detective!

In the 17th century, lens making for spectacles was a highly secretive and competitive trade. It therefore makes giving credit giving to Zaccharias Janssen and Hans Lippershay for inventing/making the early monocular and compound microscopes highly debatable. It is only known they had both filed a patent for the telescope in 1608 in the Netherlands. We presume,if a tube could house more than one lens for bringing distant objects closer, the same logic could be applied to a microscope. Thus apparently their microscope had two convex lenses aligned in a series within a sliding tube, with no stand and therefore looked like a mini telescope. By 1624, Galileo had improved upon this compound microscope with the addition of a stand, his microscope looked like a mini telescope on a stand. Not unnaturally his fellow Lincean, Giovanni Faber named it microscope (terminology obviously analogous with the telescope)! By the time Robert Hooke described the microscope he used, its main body was mounted on a wooden stand this freed both hands, the illumination came from a light source brightened by passing through a water flask and focused on the specimen using a lens, and set of screws adjusted the focus of the two lenses. Thus the basic elements of the 20th century laboratory microscope were already available. What differed was the quality of the lenses available in the 1600s.The lenses, however well crafted, were not free from optical aberrations, that allowed coloured halos to interfere with the clarity of images, in both telescopes and microscopes.

Today the website www.danda.co.uk takes you to what is now Dollond & Aitchson Limited. It was founded in 1750 by Peter Dollond and specialized in manufacture of optical instruments.264 years later, in 2014, Dollond & Aitchson is the oldest retail optical chain on High Street in London and holds major share in the optical market. Peter Dollond’s father John Dollond held the rather controversial patent for the achromatic double lens by virtue of the fact he was able to take forward and “exploit” the technology involved! John Dollond backed up the claim in 1758 by publishing an "Account of some experiments concerning the different refrangibility of light" in the Philosophical Transcations of the Royal Society. He was awarded the Copley Medal and made a fellow three years later for having constructed achromatic double lenses by combining crown and flint glasses, thereby reducing chromatic aberration. The word exploit has an interesting connotation here. The idea of the achromatic double lens apparently originated with an attorney named Chester Moore in 1733. Since Chester Moore was not an optician, he contacted two individuals to make the two different lenses to ensure secrecy. Unfortunately for Chester Moore they both outsourced the work to George Bass. The latter realizing the potential of the material in hand, apparently kept it secret till he met John Dollond who was also experimenting with achromatic lenses. Dollond patented, published and produced achromatic lenses and fine optical ware, leaving Chester Moore and Georges Bass out in the cold. 262 years later they are the oldest retail opticians on High Street in London, employing about 2500 persons with Andy Ferguson as CEO and Pradip Patel as MD. From the mid 1700s onwards, these lenses were available for telescopes but microscopes would have to wait another 50 years for the technology to evolve to craft fine small achromatic lenses suitable for microscopes.

Enter Giovanni Battista Amici, Italian instrument maker, astronomer, microscopist and botanist in the year 1824.It heralds the birth of the achromatic microscope. In England nearly concurrently worked Joseph Jackson Lister the father of Joseph Lister of antiseptic fame. He corresponded with Amici, mentioning his surprise at the near simultaneous production of short focus achromatic lenses in England and Italy. Lister knew the instrument maker William Tulley had,”executed his first good triple 0.4 inch” in 1824. Joseph Jackson Lister submitted a paper to the Royal Society “On Some Properties in Achromatic Object-Glasses Applicable to the Improvement of the Microscope” in 1831. It was the first account of fully achromatically and spherical methods for compound microscopes and stated his law of aplanatic foci. This was a culmination of his work in the mid 1820s and by the last part of that decade he had roped in William Tulley to make microscopes. Some of the big names in microscopy of the 20th century had already set up shop in the 1800s. Powell, Lealand and Smith in 1841,Carl Zeiss in 1847 and Baush and Lomb in 1853. Thus the 1800s would see wide spread use and improvement in technology and manufacture of microscopes. That it is revolutionized the nascent science of Biology as a whole and played a vital role in physical sciences is a complete understatement.

Main resources:

1. Encyclopedia Britannica
2. Wikipedia
3. https://www.zeiss.com/corporate/int/about-zeiss.htm
4. www.danda.co.uk