An ¿image¿ is a reproduction, representation or imitation of the physical form of a person or thing. It is derived from Latin word for imitate. The inventor of photography was probably the Chinese about 3000 years ago. They possessed a light sensitive material that transferred the images of leaves onto the surface of pots and vases. Englishman William Henry Fox Talbot in 1841 developed negative and positive approach of image production. Image is artificial imitation of external form of object and refers to picture and likeness of the object. Receptor refers to something that responds to the stimulus. Image receptors used in dentistry today are film, film-screen combinations, the electronic sensors used in digital imaging and computed tomography (CT). Some medical imaging systems, such as fluoroscopy systems, use X-rays as the energy source without film.