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Chester Carlson (1906-1968), American physicist, patent attorney, and inventor of xerography, an electronic dry-copying process for the reproduction of images or documents, commonly known now as photocopying.
Born in Seattle, Washington, Chester Floyd Carlson worked for a printer before studying physics at the California Institute of Technology. After graduating in 1930, he worked for a short time for the Bell Telephone Company, earned a law degree, and took a position in the patent department of an electronics firm in New York City. Carlson found it difficult to get copies of patent drawings, so in his spare time he searched for a cheap, dry method of copying documents, specifically printed or drawn matter. He developed a process that used electrostatic attraction to cause powder to adhere to plain paper, making his first successful copy on October 22, 1938. Because the process used no ink, Carlson called the technique xerography, from the Greek words meaning “dry writing.” This process is now known as photocopying.
In this process a plate coated with a light-sensitive material, such as selenium, is given a positive electric charge, and a powder, called toner, is given a negative electric charge. The toner and plate are therefore attracted to each other. Light is reflected from the original document through a lens onto the plate, and when the toner is applied to the plate, it clings to those places where light has not penetrated and destroyed the charge. In other words, the toner clings to the shadows cast by the opaque printing of the object copied. Paper is applied to the plate, and the image is transferred. Heat then fixes the toner on the paper, completing the copy. Photocopying is quick and involves no moisture—and thus it produces little mess. A variation of the process, known as xeroradiography, is used in the production of X-ray images.
Although his invention would eventually become the worldwide standard for copying, Carlson spent years securing a patent. He also had trouble finding a company willing to market the process. Finally, in 1947, the Haloid Company of Rochester, New York, obtained the rights to his invention. Working with the company, which changed its name to the Xerox Corporation, Carlson significantly refined copying for office use. In 1959 the Xerox Corporation introduced the first automatic copier.