optical sensing, in general, any method by which information that occurs as variations in the intensity, or some other property, of light is translated into an electric signal. This is usually accomplished by the use of various photoelectric devices. In one method, known as optical character recognition, a computer is given the capability of "reading" printed characters. Reflected or transmitted light from the character strikes an array of photoelectric cells, which effectively dissect it into light and dark areas. By analysis of these areas the computer is able to recognize the character, with some tolerance for less than perfect and uniform printing. Optical sensing is also used in various pattern-recognition systems, e.g., in military reconnaissance and astronomical observation; it is also used in photographic development, to enhance detail and contrast.