Seeing 20/20 in 2020


A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses, usually arranged along a common axis.

Lenses are made from glass or plastic and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing.

The word lens comes from lēns, the Latin name of the lentil, because a bi-convex lens is lentil-shaped.


Types of Lens Shapes (click image to enlarge)

Archaeological Evidence

Some scholars argue that archaeological evidence indicates that there was widespread use of lenses in antiquity, spanning several millennia. The so-called Nimrud lens is dated to the 7th century BC and may or may not have been used as a magnifying glass, or a burning glass. Others have suggested that certain Egyptian hieroglyphs depict simple glass lenses.

The Nimrud lens.

The Nimrud lens is a 3,000-year-old piece of rock crystal, which was unearthed by Sir John Layard in 1850 at the Assyrian palace of Nimrud, in modern-day Iraq.  Since its discovery over a century ago, scientists and historians have debated its use, with one prominent Italian professor claiming the lens was used by the ancient Assyrians as part of a telescope, which would explain how the Assyrians knew so much about astronomy.

Timeline: The Development of Lenses

(click on the image to enlarge or click on the link above)

Lenses in Antiquity

The oldest certain reference to the use of lenses is from Aristophanes’ play The Clouds (424 BC) which mentions a “burning glass.”

Pliny the Elder (c. 23-79 AD) confirms that burning glasses were known in the Roman period. Pliny also mentions the earliest known reference to the use of a corrective lens in his writing, noting that Nero was said to watch the gladiatorial games using an emerald (presumably concave) to correct for nearsightedness. Both Pliny and Seneca the Younger (3 BC–65 AD) described the magnifying effect of a glass globe filled with water.

Ptolemy (c. 100-170 AD) wrote a book on Optics, which was translated into Arabic and then improved upon and translated back into Latin in the 12th century. Between the 11th and 13th centuries "reading stones" were invented. These were primitive plano-convex lenses initially made by cutting a glass sphere in half.

Spectacles were invented as an improvement on "reading stones" in Northern Italy after in the late 13th century. This was the start of the optical industry of grinding and polishing lenses for spectacles, first in Venice and Florence, and later in the spectacle-making centres in both the Netherlands and Germany. Spectacle makers created improved types of lenses for correcting vision based on knowledge gained from observing the effects of the lenses.

Practical development and experimentation with lenses led to the invention of the compound optical microscope around 1595, and the refracting telescope in 1608, both of which appeared in the spectacle-making centres in the Netherlands.

Click on the artefact title to learn more.

Pair of oval-rimmed, blue-lensed spectacles.

Eyeglasses 1820-1905

ID 1956.024.010

This pair of oval-rimmed, blue lensed spectacles are a type of early safety glasses to protect one’s eyes from the sun – an early type of sunglasses. They belonged to George S. Miller (1812 - 1905), who served as Owen Sound's Harbour Master from 1877 to 1881.

A pair of goggles with green lenses and black wire mesh frames.

Goggles early 20th century

ID 1961.064.105

Theses goggles have green lenses and black wire mesh frames. They were a type of protective eyewear from either sun or wind or other natural elements that would impede sight.

Unusual pair of blue glass D shaped lensed spectacles.

Eyeglasses, 1880-1912

ID 2012.010.015                                

This unusual pair of blue-lensed spectacles are called D-Spectacles and are also known as “railway spectacles”. In the 1800s, rail travel began with passengers being carried in open-top carriages with the wind, funnel smoke and sparks from the track in their faces. Sometimes such spectacles had tinted lenses and can be seen as early sunglasses in that they were for outdoor use. 

Pair of woman's yellow plastic-framed 1940s sun glasses.

Sunglasses, 1940s                           

ID 1982.011.011                          

These yellow sunglasses are Canadian made. Starting in the 1940s, sunglasses became a popular fashion statement.

Pair of child's-sized eyeglasses with brass frames.

Eyeglasses, 1820 – 1850      

ID 1972.001.002                                               

According to the last owner, this pair of child’s-sized eyeglasses with brass frames dates to about 1825.

Pince-nez eyeglasses with SHURON impressed inside the gold bridge.

Pince-nez Eyeglasses, 1920-1940

ID 2018.020.003

Pince-nez eyeglasses dispensed from the W. J. Shortill Jewelry and Optician business of Markdale, Grey County.

Telescope with three tubes made of paper and velum.

Telescope, 1750 -1900

ID 1972.021.002                    

Also known as a spyglass, this refracting telescope is made of three tubes of paper and velum (fetal sheep skin). It was likely used on a ship for navigation or sighting land and other ships.

A round-shaped magnifying glass, with metal finger loop.

Magnifying Glass, undated             

ID 1975.083.100               

This magnifying glass has a convex lens that produces a magnified image of an object. A magnifying glass can also be used to focus light by concentrating the sun's radiation through the lens’ focus, which creates a hot spot strong enough to start a fire.  

Improved Household Microscope

Microscope, 1900 – 1925

ID 1998.005.002

This "IMPROVED HOUSEHOLD MICROSCOPE" may have been used as a school microscope as it formerly belonged to Harold Cotton, a high school teacher at West Hill Secondary School in Owen Sound.

Victorian Monocular Microscope

Microscope , 1800 - 1900

ID 1975.095.118a-v

This is a Victorian monocular microscope set. According to the last owner, it was most likely used by Owen Sound’s Dr. William Early (1863 – 1906) while he studied medicine.

Stereoscope viewer.

Stereoscope, 1904 patent

ID 1993.018.059ab

Stereoscopes were hand-held devices which allowed the user to view double-print photographs printed on cards so that the image looks somewhat three-dimensional. They can be thought of as the early predecessor of the View Master, a toy popular in the 1970s and 80s.


A single convex lens mounted in a frame with a handle or stand is a magnifying glass.

Lenses are used as prosthetics for vision correction. They are usually shaped to fit in a roughly oval frame; the optical centres are placed over the eyeballs.

Other uses are in imaging systems such as monoculars, binoculars, telescopes,  microscopes, cameras and projectors. Some of these instruments produce a virtual image when applied to the human eye; others produce a real image that can be captured on photographic film or an optical sensor, or can be viewed on a screen. 

A large lens creates enough intensity to burn a flammable object at the focal point. Since ignition can be achieved even with a poorly made lens, lenses have been used as burning-glasses for at least 2400 years. 


This exhibit was researched and developed by Owen Sound District Secondary High School co-op student, Sydney Thornton.

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