Laser Printers and LED Printers

Laser Printer and LED Printer Technology

Laser printers and LED printers share some of their technology and therefore print at high speed and with low running costs compared to Inkjet printers. A core feature of laser and LED printers is that they use an imaging drum which can be electrostatically charged, while the main difference between laser printers and LED printers is the light source which is used to put the charge onto the drum.

The diagram to the right shows the imaging drum which rotates past a light source - in either a laser printer or an LED printer - and this light source places an electrostatic charge on the drum. This charged area rotates past the toner cartridge where toner particles are attracted to the imaging drum and as the drum continues to rotate it comes into contact with the paper and transfers the toner to it. Finally, a fuser unit heats the toner and bonds it to the paper, making it permanent.

The fuser unit uses a considerable amount of current as it heats up quickly and it should be noted that laser printers and LED printers should not be plugged into the battery backup connections of a UPS (Uninterruptible Power Supply); they should be connected to the surge-only connection.

Laser Printer and LED Printer Light Sources

The LED light source in a LED printer consists of an array with thousands of individual digital LED light sources spanning the width of the image drum. These LEDs project through focusing lenses directly down on to the drum surface.

The LED array therefore does not have any rotating mirrors and is more compact compared with laser printer technology.

LED printers have an advantage over laser printers as reliability is enhanced because an LED array has no moving parts. Print quality and output speed are excellent with both colour and mono models.

A laser printer's light source and its mechanics are a little more complicated.

A  laser printer's light source consists of a large relatively heavy, but delicate, arrangement built into a large case. The case contains a single laser light source and a complex system of lenses and rotating mirrors that deflect the laser beam across the drum as it rotates.

Complex timing is used to ensure that the laser can still produce a horizontal track across the drum surface while the drum continuously rotates. The edges of the drum are further from the laser than the centre and so careful parallax correction must be employed.