A kaleidoscope is a tube with loose, small, colorful objects inside. These objects can be beads or something similar. The inside is made using three long mirrors. A person looks into the kaleidoscope through one end and sees patterns created by reflections of the objects inside.
In 1815, Sir David Brewster began work that led to the invention of the kaleidoscope. At that time, he was doing experiments on light polarization. The kaleidoscope was not patented until two years later. His first design was a tube with pairs of mirrors at one end, pairs of translucent disks at the other, and beads between the two. In 1817, Brewster chose the well-known lens developer Philip Carpenter to be the only manufacturer of the kaleidoscope. It was a big success. Two hundred thousand kaleidoscopes were sold in London and Paris in just three months. Brewster knew that the company could not make as many kaleidoscopes as people wanted. On 17 May 1818, he asked Carpenter to allow them to be made by other manufacturers. Carpenter agreed. At first, the kaleidoscope was meant to be a scientific tool. Later it was used as a toy. Brewster believed he would make money from the kaleidoscope. However, a fault in his patent application allowed others to copy it.