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Reading stone in Archeon, a historical theme park. A reading stone is an approximately hemispherical lens that can be placed over text to magnify the letters, making it easier for people with presbyopia to read. Reading stones were among the earliest common uses of lenses.
A microfilm reader is a device used in projecting and magnifying images stored in microform to readable proportions. Microform includes flat film, microfilm, aperture cards, microfiche, and ultra fiche. Using open reels or cassettes, microfilm is often used as a way to store many documents in a small space.
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A dome magnifier is a dome-shaped magnifying device made of glass or acrylic plastic, used to enlarge words on a page or computer screen. They are plano-convex lenses : the flat (planar) surface is placed on the object to be magnified, and the convex (dome) surface provides the enlargement.
The constant 25 cm is an estimate of the "near point" distance of the eye—the closest distance at which the healthy naked eye can focus. In this case the angular magnification is independent from the distance kept between the eye and the magnifying glass.
The earliest microscopes were single lens magnifying glasses with limited magnification, which date at least as far back as the widespread use of lenses in eyeglasses in the 13th century. [ 8 ] Compound microscopes first appeared in Europe around 1620 [ 9 ] [ 10 ] including one demonstrated by Cornelis Drebbel in London (around 1621) and one ...