Author: Brenton

The colour copier works in a similar fashion to the black & white device described earlier. The earlier colour copiers used colour filters in the scanning stage, to transfer varying charges onto the respective drum, as per the varying colours and density of the original. There are four drums which consist of black, yellow, cyan and magenta. Today a Charge Coupled device is used for scanning the original and laser is used to transfer light onto the drums. Each drum has its respective colour image and each image transfers onto a large image transfer belt and then onto the page, which is transported from the pickup area past the transfer belt, where the image is transfered to the page, to the fuser unit where the toner is melted onto the page using heated pressure rollers.

The Printer uses the same electronic data as the copier, but instead of it being issued from the scanner, it is issued from the computers microprocessor, and transposed to print using the same process.

Both devices may have a duplex unit for double sided copying and a collator for sorting documents.The copier may also have a document feeder to transprt multiple originals to the scanner.

There are also Multifunction Devices with Print Copy Fax and Scan

Ink is still used, as well as the powder toner process, and generally better for photo printing, but more expensive to run, and can be less reliable.

The first Xerox copier process was invented by a South Australian and the idea was sold to Xerox. The early devices were a wet process, using an electrically charged black ink. Light was reflected on to an original document via mirrors to a photosensitive drum. The drum sits in a bath of electrically charged ink and high voltage is fired at the drums surface. The result is simply high resistance in the area where there is stronger light, reflected from the original document, so a low charge, and high charge in the dark areas. The higher charge attracts more of the black ink, and the low charge, attracts less, so the image is transfered to the drum. The paper is picked up using rollers, and transported to a photosensitive drum. A second charge is emitted behind the paper, transferin the wet image onto the paper, followed by a heating process to fix the image to the page. A similar system is used today, but dry, charged pwder toner is used and melted onto the page using heated pressure rollers. A laser unit is now used to transmit the light onto the drum and light sensitive diodes are used to scan the original document.