A teleidoscope [tel-ahy-duh-skohp] is a kind of kaleidoscope, with a lens and an open view, so it can be used to form kaleidoscopic patterns from objects outside the instrument, rather than from items installed as part of it. The lens at the end of the tube is not an optical requirement, but protects the internals of the teleidoscope. A spherical ball lens is often used. An advantage of using a sphere is that it will not press flat against the object being viewed, which would block all light and result in no image being seen.
The teleidoscope was invented by John Lyon Burnside III (1916 – 2008), and because he was also responsible for the rediscovery of the math behind kaleidoscope optics, for decades, every maker of optically correct kaleidoscopes sold in the US paid him royalties.
The Daily Omnivore 
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