History of Optics - Lenses and Lensmaking

Lenses and Lensmaking

The earliest known lenses were made from polished crystal, often quartz, and have been dated as early as 700 BC for Assyrian lenses such as the Layard / Nimrud lens. There are many similar lenses from ancient Egypt, Greece and Babylon. The ancient Romans and Greeks filled glass spheres with water to make lenses.

The earliest historical reference to magnification dates back to ancient Egyptian hieroglyphs in the 5th century BC, which depict "simple glass meniscal lenses". The earliest written record of magnification dates back to the 1st century AD, when Seneca the Younger, a tutor of Emperor Nero, wrote: "Letters, however small and indistinct, are seen enlarged and more clearly through a globe or glass filled with water". Emperor Nero is also said to have watched the gladiatorial games using an emerald as a corrective lens.

Ibn al-Haytham (Alhacen) wrote about the effects of pinhole, concave lenses, and magnifying glassse in his Book of Optics. Roger Bacon used parts of glass spheres as magnifying glasses and recommended them to be used to help people read. Roger Bacon got his inspiration from Alhacen in the 11th century. He discovered that light reflects from objects and does not get released from them. Around 1284 in Italy, Salvino D'Armate is credited with inventing the first wearable eye glasses.

Between the 11th and 13th century "reading stones" were invented. Often used by monks to assist in illuminating manuscripts, these were primitive plano-convex lenses initially made by cutting a glass sphere in half. As the stones were experimented with, it was slowly understood that shallower lenses magnified more effectively.

The earliest known working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar. Galileo greatly improved upon these designs the following year. Isaac Newton is credited with constructing the first functional reflecting telescope in 1668, his Newtonian reflector.

The first microscope was made around 1595 in Middelburg in the Dutch Republic. Three different eyeglass makers have been given credit for the invention: Hans Lippershey (who also developed the first real telescope); Hans Janssen; and his son, Zacharias. The coining of the name "microscope" has been credited to Giovanni Faber, who gave that name to Galileo Galilei's compound microscope in 1625.