Chester F. Carlson

Xerography (or Electrophotography) is a photocopying technique developed by Chester Carlson in 1938 and patented on October 6, 1942. He received United States Patent number 2,297,691 for his invention. Image taken from http://www. ... A small, much-used Xerox copier in a high school library. ... Chester Carlson Chester F. Carlson (February 8, 1906 - September 19, 1968) was an American physicist, inventor, and patent attorney born in Seattle, Washington. ... 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ... October 6 is the 279th day of the year (280th in leap years). ... This article is about the year. ... A patent is a set of exclusive rights granted by a state to a person for a fixed period of time in exchange for the regulated, public disclosure of certain details of a device, method, process or composition of matter (substance) (known as an invention) which is new, inventive, and...

Xerography is used in most photocopying machines and in laser and LED printers. A small, much-used Xerox copier in a high school library. ... 1993 Apple LaserWriter Pro 630 laser printer A laser printer is a common type of computer printer that reproduces high quality text and graphics on plain paper. ... LED printers are identical in principle to laser printers except for the light source used. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

The Xerographic Process

The most common realization is an office photocopier, described here.

A metal cylinder is mounted to rotate about a horizontal axis, this is called the drum. It is about 150 mm ( 6 inches ) in diameter and the end to end dimension is the width of print to be produced plus a generous tolerance. The drum is manufactured with a surface coating of amorphous selenium (more recently ceramic or organic), by vacuum deposition. Amorphous selenium will hold an electrostatic charge in darkness and will conduct away such a charge under light.

The drum rotates at the speed of paper output. One revolution passes the drum surface through the steps described below. The drum may be a belt and there are variants at every step.

Step 1. Charging Electostatic charges are uniformly distributed over the surface of the drum by a corona discharge with output limited by a grid.

Step 2. Exposure The document to be copied is lit and passed over a lens, so that its image is projected onto the drum at exactly the same speed that the drum turns. In a laser or LED printer, a thin beam is modulated by the controller. Where there is text or image on the document, light will not penetrate to the drum; the opposite is true where there is no image. The light that penetrates releases the charge on the drum, but only where there is no image. The resulting charge that remains on the drum is called the 'latent' image and is a positive of the original document.

Step 3. Development During development, toner particles are attracted to the electrostatic latent image on the drum surface. Thus, a visible toner image is created.

Step 4. Transfer Paper is passed between the drum and the transfer corona. Because oppositely charged particles attract, the toner image is transferred from the drum or belt surface to the paper.

Step 5. Peeling Electric charges on the paper are partially neutralized by the detack saw. As a result, the paper is peeled off from the drum or belt surface.

Step 6. Fixing or Fusing The toner image is permanently fixed to the paper by heat and pressure.

Step 7. Cleaning The drum is discharged and the remaining toner is removed from the drum surface by a rotating brush under suction.

The development of xerography has led to new technologies that some predict will eventually eradicate traditional offset printing machines. These new machines that print in full CMYK color, such as Xeikon, use xerography but provide nearly the quality of traditional ink prints. Offset lithography printing process Offset printing is a widely used printing technique where the inked image is transferred (or offset) from a plate first to a rubber blanket, then to the printing surface. ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ... Under the Xeikon brand, Punch Graphix develops, manufactures and distributes high-end digital colour printing systems, the related prepress and operating software, and consumables such as toner. ...

Xerography in animation

Ub Iwerks managed to adapt xerography to eliminate the hand-inking stage in the animation process by printing the animators drawings directly to the cels. At first only black lines were possible, but in the 80's lines in different colors were introduced. The most impressive animated features to use the xerographic process are films like The Secret of NIMH and The Little Mermaid (film). A publicity photograph (circa 1929) of Ub Iwerks and his most famous co-creation, Mickey Mouse. ... This article or section does not cite its references or sources. ... The Little Mermaid is the twenty-eighth animated feature in the Disney animated features canon. ...

External links

• Encyclopedia.com's Xerography Definition
• Xerography, The invention that no one ever wanted

Further reading

"Copies in Seconds: How a Lone Inventor and an Unknown Company Created the Biggest Communication Breakthrough Since Gutenberg - Chester Carlson and the Birth of the Xerox", by David Owen