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in real time. It is meant to emulate what happens in a human, in whom the five senses gather information about the exterior world that is sent to the brain for analysis and response.An artificial brain in a blind and deaf robot body would be useless; it needs sensors that simulate the human ones, or go beyond them.

As electronic science and technology developed, they led to the construction of artificial sensors analogous to the human senses. Ma- chine vision had roots in late-nineteenth-century discoveries that light could change the electrical properties of certain materials or cause them to emit a flow of electrons; that is, an electrical current (one of these phenomena, the photoelectric effect, so baffled physicists that Albert Einstein earned a Nobel Prize in 1921 for explaining it).These effects were incorporated into devices that detected light by turning it into electricity. By the 1920s, the conversion of light into electrical signals was advanced enough that television images were being broad- cast on an experimental basis, and in the late 1930s, the BBC in En- gland and the RCA Corporation in the United States began regular television broadcasting. Improved television cameras were developed in 1939. Following World War II, commercial television broadcasting became widespread, and in 1953, color television was introduced.

Within the digital revolution brought on by the growth of com- putation, the development of video cameras whose electrical data came as a stream of binary digits was inevitable. Like a human eye that gathers data and sends it to the brain for analysis, a computer-based camera scans a scene and presents it to the computer for further pro- cessingbut this is only the beginning of meaningful machine vision. The quantity of data involved in a pictorial representation of the world is staggering and requires extremely high levels of computational power to process. And as the Shakey robot demonstrated, gathering visual data and transmitting them to the computer is the easy part; it is extraordinarily difficult to decide how to assign meaning to an image so that the robot can act on the information.

Similarly, artificial sensing of sound and means to generate it be- gan in the late nineteenth century. Between 1876 and 1878,Alexander Graham Bell patented the telephone, Thomas Edison patented the

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