The pinhole camera or camera obscura is one of the oldest optical devices.
Pinhole photography is lensless photography, ligth passes through the hole and an image is formed.
Legend has it that pinhole was discovered by an Arab who saw, on his awakening, a marvelous vision on the wall of his tent. This legend may or may not be true. Certainly the Chinese and the Greeks knew the principle of the pinhole camera and used it for observation of solar eclipses. A fair account of pinhole story and other useful information can be found in Pinhole Photography by Jon Grepstad. A Fresnel zone plate consists of a series of concentric circles whose radii are proportional to the square root of whole numbers.