How does a Laser Printer Work?

A laser printer is so-called because a laser beam is essential in its operations. It is also distinct from other printers because of its great printing speeds as well as highly accurate rendering. For instance, there are laser printers in the market that can print a hundred colored pages and two hundred non-colored pages every minute.

Components of a Laser Printer

A basic laser printer assembly has six main components. The first one is the image processor with its own memory. This image processor is programmed to convert text data into raster images which are then stored, ready for processing and printing.

The other basic components of a laser printer are the charged roller or charged corona wire, a photosensitive drum (a conveyor-like contraption), negatively charged toner, a fuser assembly and, of course, the laser assembly.

The Process of Printing

The first step to the printing process is the transmission of the data from the computer or data storage device to the printer's image processor. The image processor rasterizes the data and converts the information received into a graphic image (this is complete in color and formatting information if applicable); this image is then sent to the printer's memory in preparation for 'transmission'.

Meanwhile, the photosensitive drum is revolving and touching the charged roller or the charged corona wire. The wire or the roller imparts its negative charge to the drum and the latter acquires a negative static charge, as a result. This static charge remains on the drum's surface as long as it's dark.

At this point, the laser assembly beams light on to the revolving photocell. The laser beam passes through a series of focusing mirrors so that it would hit the drum precisely. This laser beam is activated and triggered by the data stored in the image processor memory.

At the points of the drum hit by the laser beam, the charge is reversed from negative to positive (since these areas have been exposed to light, they can no longer keep their negative charges). Through this process, the image is outlined and drawn on the drum by the laser beam; that is, the positively-charged portions of the revolving drum or photocell represent the complete image of the text or picture to be printed.

Now, the drum or the photocell touches the negatively charged toner (fine colored or black, dry powder). This toner clings to all the positively charged portions of the photocell and leaves all the negatively charged portions alone. At this point, the photocell bears the actual image.

Next, the photocell or the drum rolls over the paper and the toner is transferred to the latter. The paper with toner then passes through the fuser assembly which bonds the toner particles to the paper. Through a combination of heat (coming from a heat source within the fuser's tube) and pressure, the toner powder (made of wax or other easy to melt substance) melts on and gets bonded with the paper. The paper then comes out printed.