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Today, the photocopy widely used as in office equiments not just in printing business works. Photocopier used in daily office automation activities for business support. Color copiers might replace a black and white copiers in the future.
A photocopier (or copier) is a machine that makes paper copies of documents and other visual images quickly and cheaply unlike as the conventional printing business. Most current photocopiers use a technology called xerography, a dry process using heat. (Copiers can also use other output technologies such as ink jet, but xerography is standard for office copying.)
Xerographic office photocopying was introduced by Xerox in the 1960s, and over the following 20 years it gradually replaced copies made by Verifax, Photostat, carbon paper, mimeograph machines, and other (duplicating) printing machines. The prevalence of its use is one of the factors that prevented the development of the paperless office heralded early in the digital revolution.
Photocopying is widely used in business, education, and government. 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. However, photocopiers are undeniably more convenient than computers for the very common task of creating a copy of a piece of paper
How a photocopier works (using xerography)
Charging
The surface of a cylindrical drum is electrostatically charged by either a high voltage wire called a corona wire or a charge roller. The drum has a coating of a photoconductive material. A photoconductor is a semiconductor that becomes conductive when exposed to light.
Exposure
A bright lamp illuminates the original document, and the white areas of the original document reflect the light onto the surface of the photoconductive drum. 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. The area of the drum not exposed to light (those areas that correspond to black portions of the original document) remain negatively charged. The result is a latent electrical image on the surface of the drum. (In digital printing machines, the original document is scanned and digitized and a laser is employed to discharge the drum in a similar fashion)
Developing
The toner is positively charged. 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.
Transfer
The resulting toner image on the surface of the drum is transferred from the drum onto a piece of paper with a higher negative charge than the drum.
Fusing
The toner is melted and bonded to the paper by heat and pressure rollers.
Cleaning
The drum is wiped clean with a rubber blade and completely discharged by light. This example is of a negatively charged drum and paper, and positively charged toner as is common in today's digital copiers. Some copiers, mostly older analog copiers, employ a positively charged drum and paper, and negatively charged toner.
Invention and development
In 1937 Bulgarian physicist Georgi Nadjakov found that, when placed into an electric field and exposed to light, some dielectrics acquire permanent electric polarization in the exposed areas. That polarization persists in the dark and is destroyed in light. Chester Carlson, the inventor of photocopying, was originally a patent attorney, as well as a part-time researcher and inventor. His job at the patent office in New York required him to make a large number of copies of important papers. Carlson, who was arthritic, found this to be a painful and tedious process. As a result, he was motivated to conduct experiments with photoconductivity.
In 1949, Xerox Corporation introduced the first xerographic copier called the Model A. Xerox became so successful that, in North America, photocopying came to be popularly known as "xeroxing." Xerox has actively fought to prevent "Xerox" from becoming a genericized trademark. While the word "Xerox" has appeared in some dictionaries as a synonym for photocopying, Xerox Corporation typically requests that such entries be modified, and that people not use the term "Xerox" in this way."Photostat" is an outdated term for a photocopy. Some languages include hybrid terms, such as the widely used Polish term kserokopia ("xerocopy"), even though relatively few photocopiers are of the Xerox brand.
Xerographic copier manufacturers took advantage of a high perceived-value of the 1960s and early 1970s, and marketed paper that was "specially designed" for xerographic output. By the end of the 1970s, paper producers made xerographic "runability" one of the requirements for most of their office paper brands.Some devices sold as photocopiers have replaced the drum-based process with inkjet or transfer film technology.
Among the key advantages of photocopiers over earlier copying technologies are their ability to do the following:
> to use plain (untreated) office paper
> to implement duplex (or two-sided) printing
> to sort and/or staple output
Color photocopiers
Colored toner became available in the 1950s, although full-color copiers were not commercially available until 3M released the Color-in-Color copier in 1968, which used a dye sublimation process rather than conventional electrostatic technology. The first electrostatic color copier was released by Canon in 1973.
Color photocopying is a concern to governments, as it makes counterfeiting currency easier to accomplish. Some countries have introduced anti-counterfeiting technologies into their currency specifically to make it harder to use a color photocopier for counterfeiting. These technologies include watermarks, microprinting, holograms, tiny security strips made of plastic (or other material), and ink that appears to change color as the currency is viewed at an angle. Some photocopying machines contain special software that can prevent copying currency that contains a special pattern.
Digital technology
In recent years, all new photocopiers have adopted digital technology, thus replacing the older analog technology. With digital copying, the copier effectively consists of an integrated scanner and laser printer. This design has several advantages, such as automatic image quality enhancement and the ability to "build jobs" (that is, to scan page images independently of the process of printing them). Some digital copiers can function as high-speed scanners; such models typically offer the ability to send documents via email or to make them available on file servers.
A great advantage of digital copier technology is "automatic digital collation." When copying a set of twenty pages twenty times, for example, a digital copier scans each page only once then uses the stored information to produce twenty sets. In an analog copier, either each page is scanned twenty times (a total of 400 scans), making one set at a time, or twenty separate output trays are used for the twenty sets.
Low-end copiers also use digital technology, but they tend to consist of a standard PC scanner coupled to an inkjet or low-end laser printer, both of which are far slower than their counterparts in high-end copiers.
However, low-end scanner inkjets can provide color copying at a far lower cost than can a traditional color copier. The cost of electronics is such that combined scanner-printers sometimes have built-in fax machines.
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