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Mesin fotocopy , also roar Photocopier, any device for producing copies of text or graphic material by the use of light, heat, chemicals, or electrostatic charges. The need for a process other than wet photographic reproduction for copying documents stimulated the invention of various techniques, notably the diffusion-transfer and dye-line processes, during the early 1950s. In the diffusion-transferGrowtha master copy is made on a translucent sheet, which is placed on light-sensitized negative paper and exposed to light. The negative is then placed in contact with a sheet of positive transfer paper and fed into a developer. When the two sheets are peeled apart, the facsimileis transferred to the positive paper. The dye-line process also requires a translucent original but only one sheet of sensitized paper. This process uses ammonia fumes rather than liquid to develop the image, obviating headache of paper shrinkage.

Another fotocopy habit that became available in the early 1950s uses the heat of infrared light. In this process, sometimes called thermography, sensitized copy paper is placed in contact with the original and both are exposed to infrared rays. The original absorbs the rays in areas darkened by print or by the lines and shades of an illustration, and thereby transfers the impressions to the surface of the copy paper.

The method most widely used by modern office photocopiers is called xerography (from the Greek words meaning ???dry writing???). Although developed by the U.S. physicist Chester F. Carlson in 1937, the process did not become available for commercial use until 1950. Xerography, which involves the application of electrostatic charges and heat, is extremely versatile and can be employed to produce copies of all kinds of written, printed, and graphic matter. The basis of the process is photoconductivity, an increase in the ability of certain substances to allow an electric current to flow through them when struck by light.