In the early 1930's, a gentleman called Chester Carlson worked at a patent office in New York City. This type of work obviously involved a lot of paperwork and Carlson sought to find a way of creating a machine to make the additional copies of patent applications. He wanted to produce something which would dispense a quick, dry copy of a document. The principle would be to utilise photography with electricity. In 1935 he set up a laboratory in his own kitchen, in order to experiment.
After three hard years of work Carlson created his first photocopy, with an extremely course machine he had designed. Although the result was fairly smeared, it nonetheless proved that his technique worked. With assistance from a institute for research, Carlson soon improved his design. This printing process was named `xerography'. This name came from the Greek words for `dry writing'.
With these xerographic copiers, the user can rapidly make instantaneous copies of a variety of printed materials ranging from letters to photographs. Technical development now allows facilities to reduce, or enlarge an original document to the desired size. Some machines can produce the copy in colour and the more advanced types can even sort pages and arrange them into booklet form.
The document to be copied is placed onto a glass surface and a strong light is shone through onto the paper from within the machine. The light and dark parts of the document are picked out by the light, the light areas will reflect back while the dark areas absorb the light forming a latent image. The paper to be copied onto is then negatively charged, the non-image or light areas will lose their charge but the image or dark areas will retain it, when the toner is placed onto the paper the carbon particles stick to the charged areas turning them black. The paper is then dried by heat and ejected from the machine.
