Laser Printing

How they work

Laser printing is an electrostatic, digital printing process. It produces a high-quality text and graphics(and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively charged cylindrical drum to define a differently-charged image. The drum then selectively collects electrically charged powdered ink (toner), and transfers the image to paper, which is then heated in order to permanently fuse the text and/or imagery. As with digital photocopiers and multifunction/all-in-one inkjet printers, laser printers employ a xerographic printing process. However, laser printing differs from analog photocopiers in that the image is produced by the direct scanning of the medium across the printer photo receptor. This enables laser printing to copy images more quickly than most photocopiers.

The origins of the laser printer

Gary Starkweather was the great mind behind the laser printer. He came up with the idea in 1960 while working for the Xerox Corporation who were leading the printing market at the time. Gary worked in the product development division of the company and pitched his idea to “draw” an image using of what was to be copied directly onto the copier drum. The idea was so good that he was transferred to Palo Alto Research (Xerox PARC) in 1971. Gary adapted an Xerox 7000 copier to create SLOT (Scanned Laser Output Terminal) in 1972. Gary worked with Butler Lampson and Ronald Rider to make a control system and character generator which was later called EARS (Ethernet, Alto Research character generator, Scanned laser output terminal) which later became the Xerox 9700 laser printer.

Gary Starkweather

Colour Laser Printing

When laser printing first entered the market they printed only in monochrome/black and white. Nowadays though, colour is becoming increasingly common in laser printing. To get colour through laser printing, the paper is basically sent through the printing process four times for each of the primary printing colours; cyan, magenta, yellow and key which is black. There are multiple ways of achieving this, some laser printers placing the toner and developer units on a rotating wheel, which then the paper is sent under four times while the wheel rotates after each application. Other printers may use modified versions of this system to achieve the same goal. The advatage to using a colour laser printer over a traditional inkjet is that laser printer toners and significantly cheaper than inkjet cartriges, they are faster and more precise than other printers.

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