Photocopiers

A photocopier is an office or home machine which makes paper copies of documents and other visual images quickly and cheaply. 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 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

1. 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. The drum is coated with a photoconductive material, such as selenium. A photoconductor is a semiconductor that becomes conductive when exposed to light.
2. 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.
3. 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.
4. 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.
5. Fusing: The toner is melted and bonded to the paper by high-heat and high-pressure rollers.
6. Cleaning: The drum is wiped clean with a rubber blade and completely discharged by light before beginning the process again.
   

This example is of a negatively charged drum and paper, and positively charged toner. Some copiers employ the opposite: a positively charged drum and paper, and negatively charged toner.


Digital technology
In recent years, all new photocopiers have adopted digital technology, 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" or scan page images independently of the process of printing them. Some digital copiers can function as high-speed scanners; such models typically have the ability to send documents via email or make them available on a local area network.

The greatest advantage of a digital copier 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 a traditional color copier. The cost of electronics is such that combined scanner-printers sometimes have built-in fax machines.

Copyright issues
Photocopying material which is subject to copyright (such as books or scientific papers) is subject to restrictions in most countries. It is common practice, especially by students, as the cost of purchasing a book for the sake of one article or a few pages may be excessive. The principle of fair use (in the United States) or fair dealing (in other Berne Convention countries) allows this type of copying for research purposes.

In some countries, such as Canada, some universities pay royalties from each photocopy made at university copy machines and copy centers to copyright collectives out of the revenues from the photocopying and these collectives distribute these funds to various scholarly publishers. In the United States, photocopied compilations of articles, handouts, graphics, and other information called readers are often required texts for college classes. Either the instructor or the copy center is responsible for clearing copyright for every article in the reader and attribution information is included in the front of the reader.

Scanners

Scanner which is an office supplies in computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices. Hand-held scanners, where the device is moved by hand, were briefly popular but are now not used due to the difficulty of obtaining a high-quality image. Both these types of scanners use charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor.

Another category of office and home scanner is a rotary scanner used for high-speed document scanning. This is another kind of drum scanner, but it uses a CCD array instead of a photomultiplier.

Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects, but this type of scanner is considerably more expensive relative to other types of scanners.

Another category of scanner are digital camera scanners which are based on the concept of reprographic cameras. Due to the increasing resolution and new features such as anti-shake, digital cameras become an attractive alternative to regular scanners. While still containing disadvantages compared to traditional scanners, digital cameras offer unmatched advantages in speed and portability.

Types of scanners
Nowadays there are different types of office and home scanners depending on users purposes. Described below are the most commonly used types that can be found in the market:

1. Drum
Drum scanners capture image information with photomultiplier tubes (PMT) rather than the charged coupled device (CCD) arrays found in flatbed scanners and inexpensive film scanners. Reflective and transmissive originals are mounted to an acrylic cylinder, the scanner drum, which rotates at high speed while it passes the object being scanned in front of precision optics that deliver image information to the PMTs. Most modern color drum scanners use 3 matched PMTs, which read red, blue and green light respectively. Light from the original artwork is split into separate red, blue and green beams in the optical bench of the scanner.

The drum scanner gets its name from the large glass drum on which the original artwrok is mounted for scanning, the are usually 11"x17" in size, but maximum size varies by mauufacturer. One of the unique features of drum scanners is the ability to control sample area and aperture size independently. The sample size is the area that the scanner encoder reads to create an individual pixel. The aperture is the actual opening that allows light into the optical bench of the scanner. The ability to control aperture and sample size separately is particularly useful for smoothing film grain when scanning black and white and color negative originals.

While drum scanners are capable of scanning both reflective and transmissive artwork, a good quality flatbed scanner can produce excellent scans from reflective artwork. As a result, drum scanners are rarely used to scan prints now that high quality inexpensive flatbed scanners are readily available. Film, however, is where drum scanners continue to be the tool of choice for high-end applications. Because film can be wet mounted to the scanner drum and because of the exceptional sensitivity of the PMTs, drum scanners are capable of capturing very subtle details in film originals.

Currently only a few companies continue to manufacture drum scanners. While prices of both new and used units have come down over the last decade they still require a considerable monetary investment when compared to CCD flatbed and film scanners. However, drum scanners remain in demand due to their capacity to produce scans which are superior in resolution, color gradation and value structure. Also, since drum scanners are capable of resolutions up to 12,000 PPI, their use is generally recommended when a scanned image is going to be enlarged.

In most current graphic arts operations, very high quality flatbed scanners have replaced drum scanners, being both less expensive and faster. However, drum scanners continue to be used in high-end applications, such as museum-quality archiving of photographs and print production of high-quality books and magazine advertisements. In addition, due to the greater availability of pre-owned units many fine art photographers are acquiring drum scanners, which has created a new niche market for the machines.

The first image scanner ever developed was a drum scanner. It was built in 1957 at the US National Bureau of Standards by a team led by Russell Kirsch. The first image ever scanned on this machine was a 5 cm square photograph of Kirsch's then-three-month-old son, Walden. The black and white image had a resolution of 176 pixels on a side.

2. Flatbed
A flatbed office scanner is usually composed of a glass pane (or platen), under which there is a bright light (often xenon or cold cathode fluorescent) which illuminates the pane, and a moving optical array, whether CCD or CIS. Color scanners typically contain three rows (arrays) of sensors with red, green, and blue filters. Images to be scanned are placed face down on the glass, an opaque cover is lowered over it to exclude ambient light, and the sensor array and light source move across the pane reading the entire area. An image is therefore visible to the charge-coupled device only because of the light it reflects. Transparent images do not work in this way, and require special accessories that illuminate them from the upper side.

3. Hand
Hand office scanners are manual devices which are dragged across the surface of the image to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate would produce distorted images. They typically have a "start" button which is held by the user for the duration of the scan, some switches to set the optical resolution, and a roller which generates a clock pulse for synchronisation with the computer. Most hand scanners were monochrome, and produced light from an array of green LEDs to illuminate the image. A typical hand scanner also had a small window through which the document being scanned could be viewed. They were popular during the early 1990s and usually had a proprietary interface module specific to a particular type of computer, usually an Atari ST or Commodore Amiga.

Quality
Office scanners typically read red-green-blue color (RGB) data from the array. This data is then processed with some proprietary algorithm to correct for different exposure conditions and sent to the computer, via the device's input/output interface (usually SCSI or LPT in machines pre-dating the USB standard). Color depth varies depending on the scanning array characteristics, but is usually at least 24 bits. High quality models have 48 bits or more color depth. The other qualifying parameter for a scanner is its resolution, measured in pixels per inch (ppi), sometimes more accurately referred to as samples per inch (spi). Instead of using the scanner's true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher thanks to software interpolation. As of 2004, a good flatbed scanner has an optical resolution of 1600–3200 ppi, high-end flatbed scanners can scan up to 5400 ppi, and a good drum scanner has an optical resolution of 8000–14,000 ppi.

Manufacturers often claim interpolated resolutions as high as 19,200 ppi; but such numbers carry little meaningful value, because the number of possible interpolated pixels is unlimited. The higher the resolution, the larger the file. In most cases, there is a trade-off between manageable file size and level of detail.

The third important parameter for an office scanner is its density range. A high density range means that the office scanner is able to reproduce shadow details and brightness details in one scan.

Paper size

The international paper size standard, ISO 216, is based on the German DIN 476 standard for paper sizes. Using the metric system, the base format is a sheet of paper measuring 1 m² in area (A0 paper size). Successive paper sizes in the series A1, A2, A3, etc., are defined by halving the preceding paper size parallel to its shorter side. The most frequently used paper size is A4 (210 × 297 mm).

This standard has been adopted by all countries in the world except the United States and Canada. In Mexico, Colombia, Chile and the Philippines, despite the ISO standard having been officially adopted, the U.S. "letter" format is still in common use.

ISO paper sizes are all based on a single aspect ratio of the square root of two, or approximately 1:1.4142. The advantages of basing a paper size upon this ratio were already noted in 1786 by the German scientist Georg Lichtenberg (in a letter to Johann Beckmann): if a sheet with aspect ratio √2 is horizontally divided into two equal halves, then the halves will again have aspect ratio √2. In the beginning of the twentieth century, Dr Walter Porstmann turned Lichtenberg's idea into a proper system of different paper sizes. Porstmann's system was introduced as a DIN standard (DIN 476) in Germany in 1922, replacing a vast variety of other paper formats. Even today the paper sizes are called "DIN A4" in everyday use in Germany.

Comparison of the most common paper sizes. Click on the image to enlarge it

Laser printers

Laser printers are office supplies that have many significant advantages over other types of printers. Unlike impact printers, laser printer speed can vary widely, and depends on many factors, including the graphic intensity of the job being processed. The fastest models can print over 200 monochrome pages per minute (12,000 pages per hour). The fastest color office laser printers can print over 100 pages per minute (6000 pages per hour). Very high-speed laser printers are used for mass mailings of personalized documents, such as credit card or utility bills, and are competing with lithography in some commercial applications.

The cost of this technology depends on a combination of factors, including inflation, the cost of paper, toner, and infrequent drum replacement, as well as the replacement of other consumables such as the fuser assembly and transfer assembly. Often printers with soft plastic drums can have a very high cost of ownership that does not become apparent until the drum requires replacement.

A duplexing printer (one that prints on both sides of the paper) can halve paper costs and reduce filing volumes. Formerly only available on high-end printers, duplexers are now common on mid-range office printers, though not all printers can accommodate a duplexing unit. Duplexing can also give a slower page-printing speed, because of the longer paper path.

In comparison with the office laser printer, most inkjet and dot-matrix printers simply take an incoming stream of data and directly imprint it in a slow lurching process that may include pauses as the printer waits for more data. An office laser printer is unable to work this way because such a large amount of data needs to output to the printing device in a rapid, continuous process. The printer cannot stop the mechanism precisely enough to wait until more data arrives, without creating a visible gap or misalignment of the dots on the printed page.

Instead the image data is built up and stored in a large bank of memory capable of representing every dot on the page. The requirement to store all dots in memory before printing has traditionally limited laser printers to small fixed paper sizes such as letter or A4. Most office laser printers are unable to print continuous banners spanning a sheet of paper two meters long, because there is not enough memory available in the printer to store such a large image before printing begins.

Advantages and disadvantages of using inkjet printers

Advantages

1. Compared to earlier consumer-oriented printers, inkjets have a number of advantages. They are quieter in operation than impact dot matrix or daisywheel printers. They can print finer, smoother details through higher printhead resolution, and many inkjets with photorealistic-quality color printing are widely available.
2. In comparison to more expensive technologies like thermal wax, dye sublimations, and laser printers, inkjets have the advantage of practically no warm up time and lower cost per page (except when compared to laser printers).
3. Present-day inkjet printers use stochastic or FM screening, which gives better-quality results than low-cost laser printers when printing photographic images. Some inkjet printers print dots of more than one size, so that the screening is not purely "FM".
4. For some inkjet printers, monochrome ink sets are available either from the printer manufacturer or third-party suppliers. These allow the inkjet printer to compete with the silver-based photographic papers traditionally used in black-and-white photography, and provide the same range of tones – neutral, "warm" or "cold". When switching between full-color and monochrome ink sets, it is necessary to flush out the old ink from the print head with a special cleaning cartridge.
5. As opposed to most other types of printers, inkjet cartridges can be refilled. Most cartridges can be easily refilled by drilling a hole in and filling the tank portion of the cartridge. This method is more cost effective as opposed to buying a new cartridge each time one runs dry.
   

Disadvantages

Inkjet printers may have a number of disadvantages:

1. The ink is often very expensive (for a typical OEM cartridge priced at $15, containing 5 ml of ink, the ink effectively costs $3000 per liter)
2. Many "intelligent" ink cartridges contain a microchip that communicates the estimated ink level to the printer; this may cause the printer to display an error message, or incorrectly inform the user that the ink cartridge is empty. In some cases, these messages can be ignored, but many inkjet printers will refuse to print with a cartridge that declares itself empty, in order to prevent consumers from refilling cartridges.
3. The lifetime of inkjet prints is limited; they may eventually fade and the color balance may change.
4. Because the ink used in most inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of water, which can cause severe "blurring" or "running." Similarly, water-based highlighter markers can blur inkjet-printed documents.
   

These disadvantages have been addressed in a variety of ways:

1. Third-party ink suppliers sell ink cartridges at significantly reduced costs (often 10%-30% of OEM cartridge prices) and also sell kits to refill cartridges, and bulk ink, at even lower prices.
2. Many vendors' "intelligent" ink cartridges have been reverse-engineered. It is now possible to buy inexpensive devices to reliably reset such cartridges to report themselves as full, so that they may be refilled many times.
3. Print lifetime is highly dependent on the quality and formulation of the ink, as well as the paper chosen. The earliest inkjet printers, intended for home and small office applications, used dye-based inks. Even the best dye-based inks are not as durable as pigment-based inks, which are now available for many inkjet printers
   

5 Star Value Copier Paper

I was shopping for office supplies the other day and was surprised to find that euroffice was offering some cheap and excellent 5 Star Value Copier Paper.

Office supplies

Office supplies is the generic term that refers to all supplies regularly used in offices by businesses and other organizations, from private citizens to governments, who works with the collection, refinement, and output of information (colloquially referred to as "paper work").

The term office supplies includes small, expendable, daily use items such as paper clips, staples, hole punches, binders, laminators, writing utensils and paper, but also encompasses higher-cost equipment like computers, printers, fax machines and photocopiers, as well as office furniture.