Parfocal length

Obsidian mirrors from 6,200 BCE were discovered at Catal Huyuk, the ancient city near modern-day Konya, Turkey.  People in Iran used polished copper mirrors at least as early as 4,000 BCE.  In what is now Iraq, one Sumerian noble-woman from about 2,000 BCE called "the Lady of Uruk" had a mirror made of pure gold, according to a cuneiform tablet discovered in the ruins of that city.  In the Bible, Isaiah scolds Israelite women who were "haughty and walk[ed] with necks outstretched, ogling and mincing as they go..."  He warns them that God will do away with all of their finery - and their brass mirrors!

For much more information on mirrors, as well as many other interesting topics, see Mark Pendergrast's book Mirror Mirror: A History of the Human Love Affair with Reflection, (Basic Books, 2004).

But what about the glass mirror we know today?  It also came about surprisingly early. Who was it, then, that made a sheet of glass, backed with metal, into a perfect reflecting surface?

Working distance A is the distance between the entrance aperture's central axis and the working plane. A is determined by the focal length and mounting position of the F-Theta objective (if present). For prefocus systems, working distance A is determined by the dynamic focusing unit in the null position ("z=0" plane).

These early experiments in the art were not flat, so they must have been a bit like fun-house mirrors. (Users' noses probably looked enormous!) In addition, early glass was generally somewhat bubbly and discolored.

Working distanceof lens

To make a mirror, pre-Christian Lebanese or Phoenicians blew a thin sphere of molten glass into a bubble, and then poured hot lead into the bulb of glass. The lead coated the inside of the glass. When the glass cooled, it was broken and cut into convex pieces of mirror.

As far as we know, the first mirror-makers lived near the city of Sidon, Lebanon, some 2,400 years ago.  Since glass itself likely was invented in Lebanon, it's not too surprising that it was the site of the earliest modern mirrors. Unfortunately, we do not know the name of the tinkerer who first came up with this invention.

By transforming lasers into universal tools, scanning solutions help to add functionality and value to materials. SCANLAB's broad palette of scanning solutions fulfills demands for higher speed, more precision, greater efficiency or improved environmental compatibility.

Working distancemicroscope

A Chinese source from 673 BCE casually mentions that the queen wore a mirror at her girdle, indicating that this was a well-known technology there, as well.  The earliest mirrors in China were made from polished jade; later examples were made from iron or bronze.  Some scholars suggest that the Chinese acquired mirrors from the nomadic Scythians, who were in contact with Middle Eastern cultures as well, but it seems just as likely that the Chinese invented them independently.

Nonetheless, the images would have been much clearer than those obtained by looking into a sheet of polished copper or bronze. The blown bubbles of glass used were thin, minimizing the impact of the flaws, so these early glass mirrors were a definite improvement over earlier technologies.

The Phoenicians were masters of the Mediterranean trade routes, so it's no surprise that this wonderful new trade object quickly spread throughout the Mediterranean world and the Middle East.  The Persian emperor Darius the Great, who ruled around 500 BCE, famously surrounded himself with mirrors in his throne room to reflect his glory.  Mirrors were used not only for self-admiration, but also for magical amulets.  After all, there's nothing like a clear glass mirror to repel the evil eye!

Mirrors were commonly thought to reveal an alternate world, in which everything was backward.  Many cultures also believed that mirrors could be portals into supernatural realms.  Historically, when a Jewish person died, his or her family would cover all of the mirrors in the household to prevent the deceased person's soul from being trapped in the mirror.  Mirrors, then, were very useful but also perilous items!

Free working distance A' is the mechanical distance between the scan system (bottom edge of housing including objective) and the "z=0" working plane.

Who invented the first mirror?  Humans and our ancestors probably used pools of still water as mirrors for hundreds of thousands or even millions of years. Later, mirrors of polished metal or obsidian (volcanic glass) gave wealthy preeners a more portable view of themselves.

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