HISTORY OF THE MICROSCOPE

ANCIENT HISTORY

From ancient times, man has wanted to see things far smaller than could be perceived with the naked eye. Although the first use of a lens is a bit of a mystery, it’s now believed that use of lenses is more modern than previously thought.However, it has been known for over 2000 years that glass bends light. In the 2nd Century BC, Claudius Ptolemy described a stick appearing to bend in a pool of water, and accurately recorded the angles to within half a degree. He then very accurately calculated the refraction constant of water.During the 1st century AD (year 100), glass had been invented and the Romans were looking through the glass and testing it. They experimented with different shapes of clear glass and one of their samples was thick in the middle and thin on the edges.They discovered that if you held one of these “lenses” over an object, the object would look larger. These early lenses were called magnifiers or burning glasses. The word lens is actually derived from the Latin word lentil, as they were named because they resembled the shape of a lentil bean.At the same time, Seneca described actual magnification by a globe of water. “Letters, however small and indistinct, are seen enlarged and more clearly through a globe of glass filled with water.” The lenses were not used much until the end of the 13th century when spectacle makers were producing lenses to be worn as glasses. Then, around 1600, it was discovered that optical instruments could be made by combining lenses.

The early simple “microscopes” which were only magnifying glasses had one power, usually about 6x – 10x. One thing that was very common and interesting to look at, were fleas and other tiny insects, hence these early magnifiers called “flea glasses”.Sometime, during the 1590’s, two Dutch spectacle makers, Zaccharias Janssen and his father Hans started experimenting with these lenses. They put several lenses in a tube and made a very important discovery. The object near the end of the tube appeared to be greatly enlarged, much larger than any simple magnifying glass could achieve by itself!Their first microscopes were more of a novelty than a scientific tool since maximum magnification was only around 9X and the images were somewhat blurry. Although no Jansen microscopes survived, an instrument made for Dutch royalty was described as being composed of “3 sliding tubes, measuring 18 inches long when fully extended, and two inches in diameter”. The microscope was said to have a magnification of 3x when fully closed, and 9x when fully extended.It was Antonie Van Leeuwenhoek (1632-1723), a Dutch draper and scientist, and one of the pioneers of microscopy who in the late 17th century became the first man to make and use a real microscope.He made his own simple microscopes, which had a single lens and were hand-held. Van Leeuwenhoek achieved greater success than his contemporaries by developing ways to make superior lenses, grinding and polishing a small glass ball into a lens with a magnification of 270x, the finest known at that time (other microscopes of the time were lucky to achieve 50x magnification). He used this lens to make the world’s first practical microscope.

Leeuwenhoek’s microscope used a single convex glass lens attached to a metal holder and was focused using screws. Anthony Leeuwenhoek became more involved in science and with his new improved microscope was able to see things that no man had ever seen before. He saw bacteria, yeast, blood cells and many tiny animals swimming about in a drop of water. People did not realize that magnification might reveal structures that had never been seen before – the idea that all life might be made up of tiny components unseen by the unaided eye was simply not even considered.

Source : https://www.visioneng.com/history-of-the-microscope/