How did spectacles originate?

Around 1000AD, the first vision aid was invented, called a reading stone, which was a glass sphere that was laid on top of the material to be read that magnified the letters.

Around 1284 in Italy, Salvino D’Armate is credited with inventing the first wearable eye glasses. The ingenious American inventor Benjamin Franklin invented bifocal spectacles in 1784. he was getting old, and was having trouble seeing objects both close up and at a distance. He grew so tired of switching two different pairs of spectacles, so he devised a way to have both type of lenses fit into a single frame. The distance lens was placed at the top, and the up-close lens was placed at the bottom. Bifocal spectacles are made this way even today.

The oldest known lens was found in the ruins of ancient Nineveh, and was made of polished rock crystal, 4 cm in diameter.

Around the year 1752, eyeglass designer James Ayscough introduced his spectacles with double-hinged side pieces. The lenses were made of tinted glass as well as clear. Ayscough felt that white glass created an offensive glaring light that was bad to the eyes. He advised the use of green and blue glasses. Ayscough glasses were the first sunglass like eye-glasses, but they were not made to shield the eyes from the sun, they corrected for vision problems.

Edwin H. Land invented a cellophane-like polarizing filter (patented in 1929), the first modern filters to polarize light. Polarizing celluloid became the critical element in polarizing sunglass lenses; it is a process that reduces light.

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