I. Laser printers and their types
In terms of printing principles, the most common printers on the market can be broadly categorized into inkjet printers, laser printers, and dot matrix printers. Compared to other types of printers, laser printers have several significant advantages, including faster printing speeds, better print quality, and lower operating noise. Furthermore, with continuously decreasing prices, they are now widely used in office automation (OA) and various computer-aided design (CAD) systems.
Laser printers can be broadly categorized into monochrome laser printers and color laser printers. The decline of dot matrix printers in the business office sector has created a significant opportunity for monochrome laser printers to become the preferred choice for enterprise IT infrastructure. However, they are now caught in the crossfire between inkjet printers and multifunction printers. The most prominent features of monochrome laser printers are their excellent print quality, low printing costs, superior work efficiency, and extremely high print volume, which ensures they remain the mainstream in today's office printing market. Although monochrome laser printers are more expensive than inkjet printers and have fewer features than multifunction printers, they have a clear advantage in terms of cost per page and printing speed, making them the preferred choice for efficiency-conscious business professionals. With the development of the Internet, future monochrome laser printers will no longer be simple, standalone peripheral devices with printing capabilities, but will gradually evolve into intelligent, automated document processing and output terminals operating within the network.
II. Working Principle of Laser Printers
A laser printer uses pulsed laser light emitted by a laser generator to scan a black and white printing paper through a medium such as a ribbon and a pad. Also known as a laser inkjet printer, it's a device that uses a laser printhead as the printing medium, a laser as the heat source, and inkjet printing ink to perform non-contact printing of images and text. Compared to traditional printers, it offers faster printing speeds, clearer images, and lower costs. Its working principle involves using two ribbons to copy the images from black and white and color printing paper onto two separate sheets, then placing the two sheets together for scanning and copying.
The main difference between inkjet printers and laser printers is that the printhead of an inkjet printer is in contact with the ink, while the printhead of a laser printer is not in contact with the ink.
III. Laser Printer Working Process
The composition, design structure, control methods, and components used in the control devices and parts required for laser printer operation vary depending on the brand and model. For example:
① The polarity of the charge on the photosensitive drum is different.
② The components used for charging the photosensitive drum differ. Some models use electrode wire discharge to charge the photosensitive drum, while others use a charging roller (FCR) to charge the photosensitive drum.
③ The components used in high-pressure transfer printing are different.
④ The exposure methods for the photosensitive drum differ. Some models use a scanning mirror to directly scan and expose the photosensitive drum, while others use a reflected laser beam after scanning to expose the photosensitive drum.
However, their working principles are basically the same. The laser beam emitted by the laser is reflected by a mirror and enters the acousto-optic deflection modulator. At the same time, binary graphic dot matrix information sent by the computer is sent from the interface to the character generator to form binary pulse information of the required character shape. The signal generated by the synchronizer controls nine high-frequency oscillators, which are then fed into the acousto-optic modulator through a frequency synthesizer and a power amplifier to modulate the laser beam entering through the mirror. The modulated beam enters a multi-faceted rotating mirror, and then is focused by a wide-angle focusing lens onto the surface of the photoconductor drum (selenium drum), changing the angular velocity scan into a linear velocity scan, thus completing the entire scanning process.
The drum surface is first charged by charging electrodes to obtain a certain potential. Then, after exposure by a laser beam carrying graphic information, an electrostatic latent image is formed on the drum surface. After development by a magnetic brush developer, the latent image is transformed into a visible toner image. When passing through the transfer zone, under the action of the electric field of the transfer electrodes, the toner is transferred onto plain paper. Finally, after passing through a preheating plate and a high-temperature hot roller for fixing, the text and images are fused onto the paper. After printing the graphic information, a cleaning roller removes any untransferred toner, an anti-static lamp removes residual charge from the drum, and a cleaning paper system performs a thorough cleaning before starting a new work cycle.
