A copier (also known as copier or copier ) is a machine that makes copies of paper documents and other visual images quickly and cheaply. Most photocopiers today use a technology called xerography , a dry process that uses electrostatic charges on a light-sensitive photoreceptor to first pull and then transfer the toner particles (powder) onto the paper in the form of an image. Heat, pressure or a combination of both are then used to hold the toner to paper. (Photocopiers can also use other technologies such as ink jets, but xerography is the standard for office copying.) Previous versions include the Gestetner stencil duplicator, created by David Gestetner in 1881.
Photocopier commercial xerographic office was introduced by Xerox in 1959, and gradually replaced the copy made by Verifax, Photostat, carbon paper, stencil machine, and other duplicating machines.
Photocopies are widely used in business, education, and government sectors. Although there is a prediction that photocopiers will eventually become obsolete as information workers increase their use of digital document creation, storage and distribution, and less dependent on distributing actual pieces of paper, by 2015, photocopiers continue to be widely used. In 2010, there was convergence in some high-end machines between the role of copiers, fax machines, scanners, and printers connected to computer networks to multi-function printers. Lower-end machines that can copy and print colors have increasingly dominated the home-office market as their prices continue to fall through 2017. More sophisticated color photocopiers capable of handling heavy duty cycles and large format printing remain a more expensive specialty for print and design shop.
Video Photocopier
Histori
Chester Carlson, the inventor of photocopy, was originally a patent lawyer, as well as part-time researcher and inventor. His work at the patent office in New York required him to make a large number of important papers. Carlson, who suffers from arthritis, considers this a painful and tedious process. This motivated him to experiment with photo conductivity. Carlson used his kitchen for "electrophotography" experiments, and, in 1938, he applied for a patent for the process. He made the first photocopy using a zinc-coated zinc plate. The words "10-22-38 Astoria" are written on a microscope slide, which is placed above more sulfur and under bright light. After the slide is removed, the mirror image of the words remains. Carlson tried to sell his invention to several companies, but failed because the process is still undeveloped. At that time, many of the most common copies were made at the origin of the document, using carbon paper or manual duplication machines, and people did not see the need for an electronic machine. Between 1939 and 1944, Carlson was rejected by more than 20 companies, including IBM and General Electric - no one believes there is a significant market for photocopiers.
In 1944, the Battelle Memorial Institute, a nonprofit organization in Columbus, Ohio, contracted Carlson to refine his new process. Over the next five years, the institute is conducting experiments to improve the electrophotography process. In 1947, Haloid Corporation (a manufacturer and seller of small photo paper in New York) approached Battelle to obtain a license to develop and market a photocopier based on this technology.
Haloid feels that the word "electrophotography" is too complicated and does not have a good recall value. After consulting a classic language professor at Ohio State University, Haloid and Carlson changed the process name to "xerography," which comes from Greek words meaning "dry writing." Haloid calls the new copiers "Xerox Machines" and, in 1948, the word "Xerox" is a trademark. Haloid finally changed its name to Xerox Corporation.
In 1949, Xerox Corporation introduced the first xerographic photocopiers called Model A. Xerox to be so successful that, in North America, photocopying became popularly known as "xeroxing." Xerox has been actively struggling to prevent "Xerox" being a generic trademark. While the word "Xerox" has appeared in some dictionaries as a synonym for photocopying, Xerox Corporation usually requests that the entry be modified, and people do not use the term "Xerox" in this way. Some languages ​​include hybrid terms, such as the widely used Polish term kserokopia ("xerocopy"), although relatively few copiers of the Xerox brand.
In the early 1950s, Radio Corporation of America (RCA) introduced variations on a process called Electrofax, in which images were formed directly on special coated paper and supplied with toner dispersed in liquid.
During the 1960s and up to the 1980s, Savin Corporation developed and sold liquid toner photocopiers that applied technology based on patents held by the company.
Prior to the widespread adoption of xerographic photocopiers, direct copies of photographs manufactured by machines like Kodak's Verifax were used. The main obstacle associated with pre-xerographic copying technology is the high cost of inventory: Verifax printing requires inventory at USD $ 0.15 in 1969, while Xerox printing can be made for USD $ 0.03 including paper and labor. Coin-operated Photostat machines still found in some public libraries in the late 1960s made letter-size copies for USD $ 0.25 each, when the minimum wage for US workers was USD $ 1.65 per hour; Xerox machines that replace them are usually charged USD $ 0.10.
The Xerographic copiers took advantage of the high perceived value of the 1960s and early 1970s, and marketed a "custom-designed" paper for xerographic output. In the late 1970s, paper manufacturers made "sticking" xerography as one of the requirements for most of their office paper brands.
Some devices sold as copiers have replaced drum-based processes with inkjet technology or film transfer.
Among the main advantages of photocopying machines compared to previous copying technology is its ability:
- to use plain (unprocessed) office paper,
- to implement duplex (or two-sided) printing,
- Can scan multiple pages automatically with ADF, and
- in the end, to sort and/or menstaples the output.
Photocopy of color
Colored toners became available in the 1950s, although full-color copiers were not commercially available until 3M released the Color-in-Color copier in 1968, using dye dyeing processes rather than conventional electrostatic technology. The first electrostatic color photocopier was released by Xerox (6500) in 1973. Color photocopying is a problem for governments, as it facilitates counterfeiting of currencies and other documents: for more information see the Forgery section.
Digital technology
There is an increasing tendency for new copiers to adopt digital technology, thus replacing older analogue technologies. With digital copying, photocopiers effectively consist of an integrated scanner and laser printer. This design has several advantages, such as improved image quality automatically and the ability to "build jobs" (ie, to scan a page image separately from the printing process). Some digital copiers can serve as high-speed scanners; Such models usually offer the ability to send documents via email or make them available on the file server.
The great advantage of digital copier technology is "automatic digital gathering." For example, when copying a set of 20 pages 20 times, the digital copier scans each page only once, then uses the stored information to produce 20 sets. In analog copiers, each page is scanned 20 times (400 total scans), make one set at a time, or 20 separate output trays are used for 20 sets.
Low-end copiers also use digital technology, but tend to consist of standard PC scanners that are incorporated into low-end inkjet or laser printers, both much slower than their counterparts in high-end copiers. However, low-end scanner-inkjets can provide color copying at lower purchase prices but at a much higher cost per copy. Electronic costs are such that combined scanners sometimes have built-in fax machines. (See the Multifunctional printer.)
Maps Photocopier
How it works (using xerography)
- Charging : an electrostatic cylinder drum is charged by a high-voltage wire called a corona wire or charge roller. The drum has a layer of photoconductive material. Photoconductors are semiconductors that become conductive when exposed to light.
- Lighting : The bright light illuminates the original, and the white area of ​​the original documents reflects light onto the surface of the photoconductive drum. The exposed drum area becomes conductive and is therefore discharged to the ground. The non-exposed drum area (the area corresponding to the black part of the original) remains negatively charged.
- Develop : Toner is positively charged. When applied to the drum to develop the image, it is attracted and attached to a negatively charged area (black area), such as a paper attached to a balloon with a static charge.
- Transfer : The resulting toner image on the drum surface is transferred from the drum to a piece of paper with a higher negative charge than the drum.
- Merging : Toner is melted and tied to paper with hot rolls and pressure.
A negative photocopy reverses the color of the document when making a copy, producing a white-looking letter on a black background instead of black on a white background. Negative copies of old or faded documents sometimes produce documents that are better focused and easier to read and learn.
Copyright issues
Copyrighted material that is subject to copyright (such as books or scientific papers) is subject to restrictions in most countries. This is a common practice, because the cost of purchasing a book after another article or multiple pages can be overkill. The principle of fair use (in the United States) or fair transactions (in other Berne Convention countries) allows copying for specific purposes.
In certain countries, such as Canada, some universities pay royalties from each photocopy made at university photocopiers and photocopy centers to a collection of copyright from earnings from photocopies, and collectively distribute generated funds to various academic publishers. In the United States, compilations of copies of articles, leaflets, graphics, and other information called readers are often requested for the lecture class. Either the instructor or copying center is responsible for removing the copyright for each article in the reader, and the attribution information must be clearly included in the reader.
Forgery
To address the risk of people using color copiers to make copies of counterfeit currency, some countries have incorporated anti-counterfeiting technology into their currency. These include watermarks, microprinting, holograms, small security strips made of plastic (or other materials), and inks that seem to change color because the currency is seen at an angle. Some copiers contain special software that can prevent copying of currencies containing special patterns.
Color copying also raises concerns related to copying and/or forging other documents, such as driver licenses and university degrees and transcripts. Some driver licenses are made with an embedded hologram so that police officers can detect fake copies. Some university and college transcripts have a special anti-copy watermark in the background. If a copy is made, the watermark will become very visible, allowing the recipient to specify that they have a copy of the original original transcript.
Health issues
Exposure to ultraviolet light is a concern. In the early days of photocopiers, sensitive light sources were filtered to green to match the optimum sensitivity of the photoconductive surface. This filter easily removes all ultraviolet. Currently, various light sources are used. Because the glass transmits ultraviolet light between 325 and 400 nanometers, photocopiers with ultraviolet-producing lights such as fluorescent, tungsten halogen, or xenon flash, expose the document to some ultraviolet.
Concerns about emissions from photocopiers have been revealed by some in connection with the use of selenium and the emission of ozone and smoke from heated toners.
Forensic identification
Similar to forensic typewriter identification, computer printers and copiers can be tracked by imperfections in their output. The mechanical tolerance of the toner and paper feeding mechanism leads to milkfish, which can reveal information about the mechanical properties of individual devices. It is often possible to identify manufacturers and brands, and, in some cases, individual printers can be identified from a set of printers known by comparing their output.
Some color printers and steganographically-qualified copiers impart their identification code to a printed page, as a subtle and almost invisible pattern of yellow dots. Some sources identify Xerox and Canon as companies that do this. The Electronic Frontier Foundation (EFF) has investigated this issue and documented how the Xerox DocuColor printer serial number, as well as the print date and time, is encoded in a recurring 8 - 15 dot pattern in the yellow channel. EFF serves to reverse engineer additional printers. The EFF also reports that the US government has asked these companies to implement such a tracking scheme, so that forgery can be tracked. The EFF has submitted a Freedom of Information Act request to see the privacy implications of this tracking.
See also
- List of duplicates
- Heliography
- Reprography
- Risograph
- Scanography
- Thermochromatic ink
- Thermofax
- Xerox Art
- Gestetner
References
Further reading
- R. Schaffert: Electrophotography . Focal Press, 1975
- Owen, David (August 2004). Copy in Seconds: How The Inventors of Lone and Unknown Companies Created the Largest Communication Breakthrough Since Gutenberg: Chester Carlson and the Birth of Xerox Machines . New York: Simon & amp; Schuster. ISBNÃ, 0-7432-5117-2.
Source of the article : Wikipedia
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