4/3/2023 0 Comments Photocopy example![]() ![]() When it is applied to the drum to develop the image, it is attracted and sticks to the areas that are negatively charged (black areas), just as paper sticks to a toy balloon with a static charge. Developing: The toner is positively charged.The result is a latent electrical image on the surface of the drum. The area of the drum not exposed to light (those areas that correspond to black portions of the original document) remains negatively charged. The areas of the drum that are exposed to light (those areas that correspond to white areas of the original document) become conductive and therefore discharge to ground. ![]() Exposure: A bright lamp is shined onto the original document, and the white areas of the original document reflect the light onto the surface of the photoconductive drum.A photoconductor is a semiconductor that becomes conductive when exposed to light. The drum is coated with a photoconductive material, such as selenium. Charging: The surface of a cylindrical drum is given an electrostatic charge by either a high voltage wire called a corona wire or a charge roller.Schematic overview of the xerographic photocopying process (steps 1–4). How a photocopier works (using xerography) In the early 1950s, RCA (Radio Corporation of America) introduced a variation on the process called Electrofax where images are formed directly on specially coated paper and rendered with a toner dispersed in a liquid. After consulting a professor of classical language at Ohio State University, Haloid and Carlson changed the name of the process to "Xerography," derived from Greek words that meant "dry writing." Haloid decided to call the new copier machines "Xerox," a name that was trademarked in 1948. Haloid felt that the word "electrophotography" was too complicated and did not have good recall value. In 1947, Haloid (a small New York-based organization manufacturing and selling photographic paper at that time) approached Battelle to obtain a license to develop and market a copying machine based on this technology. Over the next five years, the institute conducted experiments to improve the process of electrophotography. In 1944, the Battelle Memorial Institute, a non-profit organization in Columbus, Ohio, contracted with Carlson to refine his new process. Between 19, Carlson was turned down by over 20 companies, including IBM and GE, neither of which believed there was a significant market for copiers. At the time multiple copies were made using carbon paper or duplicating machines and people did not feel the need for an electronic machine. Carlson tried to sell his invention to some companies, but because the process was still underdeveloped he failed. After the slide was removed, a mirror image of the words remained. The words "10-22-38 Astoria" were written on a microscope slide, which was placed on top of more sulfur and under a bright light. He made the first "photocopy" using a zinc plate covered with sulfur. Carlson experimented with "electrophotography" in his kitchen and in 1938, applied for a patent for the process. This prompted him to conduct experiments with photoconductivity. ![]() Carlson, who was arthritic, found this a painful and tedious process. His job at the patent office in New York required him to make a large number of copies of important papers. That polarization persists in the dark and is destroyed in light.Ĭhester Carlson, the inventor of photocopying, was originally a patent attorney and part-time researcher and inventor. In 1937, Bulgarian physicist Georgi Nadjakov found that when placed in an electric field and exposed to light, some dielectric materials acquire permanent electrical polarization in the exposed areas. However, photocopiers are undeniably more convenient than computers for the very common task of creating a copy of a piece of paper. There have been many predictions that photocopiers will eventually become obsolete as information workers continue to increase their digital document creation and distribution and rely less on distributing actual pieces of paper. ![]() Photocopying is widely used in business, education, and government. ![]()
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