This article explains in more detail the basic working principle of laser printers on the market. Since many digital printing devices also use this technology, it is hoped that this article will be helpful to friends who use digital devices.

basic structure

Laser printers are composed of lasers, acousto-optic modulators, high-frequency drivers, scanners, synchronizers, and optical deflectors. Their function is to modulate the binary matrix information sent from the interface circuit to the laser beam, and then to scan the light. Physically. The photoreceptor and the photoconductor constitute an electrophotographic transfer system, and the photo image projected on the photoreceptor drum is transferred onto the print paper, and the principle is the same as that of the copying machine. Laser printers are non-hit output devices that combine laser scanning technology with electronic imaging technology. Its model is different, the printing function also has the difference, but the working principle is basically the same, must pass through: Charging, exposes, develops, transfers, eliminates electricity, cleans, the fixing seven processes, among them has five processes are carries on the photosensitive drum . When the text or image to be printed is input into the computer, it is preprocessed by computer software. Then the printer driver converts the print command (printer language) recognized by the printer to the high-frequency drive circuit to control the laser emitter on and off, forming a laser beam, and then scanning the mirror to the electronic display system. The photosensitive drum in the axial scanning exposure, the longitudinal scan is achieved by the photosensitive drum's own rotation.

Photosensitive drum is a photosensitive device that has light-conducting properties. The photoconductive coating on the surface is charged by the charging roller with uniform charge before scanning exposure. When the laser beam is scanned into the photosensitive drum in the form of a dot matrix, the scanned spot is turned on due to exposure, and the charge is rapidly released from the conductive substrate to the ground. The unexposed spots still maintain the original charge, thus forming a potential latent image (electrostatic latent image) on the surface of the drum, when the drum with the electrostatic latent image is rotated to the position where the toner magnetic roller is loaded. The oppositely charged toner is adsorbed on the surface of the drum to form a toner image.

When the photosensitive drum carrying the toner image continues to rotate to reach the image transfer device, a piece of printing paper is also fed to the middle of the photosensitive drum and the image transfer device. At this time, the image transfer device applies a strong voltage to the back of the printing paper. The toner image on the photoconductor drum is attracted to the printing paper, and the paper bearing the toner image is sent to a high-temperature fixing device for warming, pressure hot-melting, the toner is melted and immersed in the printing paper, and finally output Is the printed text or image.

The composition, design structure, control method, and components used for the control devices and components required for the laser printer work process may differ depending on the brand and model, such as:

1 The polarity of charging the drum is different.

2 Drum charging uses different parts. Some models use a wire discharge method to charge the drum, and some models use a charge roller (FCR) to charge the drum.

3 The components used for high pressure transfer are different.

4 photosensitive drum exposure in different forms. Some models use a scanning mirror to scan and expose the photosensitive drum directly, and some models use a reflected laser beam after scanning to expose the photosensitive drum.

However, their working principle is basically the same. The laser beam emitted by the laser is injected into the acousto-optic deflection modulator via the mirror. At the same time, the binary graphics information sent from the computer is sent from the interface to the font generator to form the binary pulse of the desired font. Information, the signal generated by the synchronizer controls the 9 high-frequency oscillators, and is added to the acousto-optic modulator via the frequency synthesizer and power amplifier to modulate the laser beam injected by the mirror. The modulated light beam enters the polygon mirror, and is focused by the wide-angle focusing lens and then hits the surface of the photoconductor drum (toner drum) so that the angular velocity scan becomes a linear velocity scan and the entire scanning process is completed.

The surface of the drum is first charged by the charging pole to obtain a certain potential, and then the latent image is formed on the surface of the drum by the exposure of the laser beam carrying the image and image information, and the latent image is transformed into a latent image by the magnetic brush developer. The visible toner image passes through the transfer area. Under the effect of the electric field of the transfer electrode, the toner is transferred to the plain paper. Finally, the toner is fused on the paper by the preheated plate and the high-temperature heat roller. Text and images. Before printing the graphic information, the cleaning roller removes the toner that has not been transferred, the erasing lamp removes the residual charge on the drum, and is thoroughly cleaned by the cleaning paper system to enter a new working cycle.