Structure and working principle of laser printers
The basic structure of
Laser printer is a laser, acousto-optic modulator, high-frequency drive, scanners, synchronizer and optical deflection, etc., whose role is to interface circuits of information sent by the binary lattice modulation in the laser beam on the photoreceptor after the scan body on. Photosensitive body and photographic agencies electrophotographic transfer systems, to reach all parts of a graphic image on a photosensitive drum transfer to the print paper, the same as its principle and copier. Laser printer is the laser scanning technology and electronic imaging technology, a combination of non-impact output device. It models different printing functions are also different, but works basically the same, must go through: charging, exposure, developing, transfer, consumption of electricity, cleaning, fixing seven processes, of which five process is carried out around the photosensitive drum . When you want to print text or image input to the computer, through computer software to its pre-process. Then the printer driver into the printer can identify the print command (printer language) sent to the high-frequency drive circuit to control the laser transmitter of the open and shut to form a lattice laser beam, and then by scanning rotating mirror system for electronic imaging The photosensitive drum axial scanning exposure, the vertical scanning by the photosensitive drum to achieve the self-rotation.
Photosensitive drum is a photosensitive device, there by the light conduction characteristics. Photoconductive coating the surface of the scanning exposure ago by the charging roller uniformly charging the charge. When the laser beam in the form of dot-matrix to the photosensitive drum when the fire was a result of exposure of the scanned point turn, charge from the conductive base pairs in the prompt release. There is no point of exposure remains the original charge, so that the surface of photosensitive drum to form a potential difference of the latent image (electrostatic latent image), when with the electrostatic latent image of the photosensitive drum rotating magnetic roller to the toner containing the location of with the opposite charge of the toner is adsorbed to the photosensitive drum of the toner image formed on the surface.
When the toner image containing the photosensitive drum continues to rotate, to reach the image transfer device, a printing paper also be sent to photosensitive drum with the image transfer device in the middle, this time the image transfer device in the printing paper on the back of a strong release voltage, the toner on the photosensitive drum as to attract to the print paper, and then carrying toner images printed on paper into the high temperature fuser unit heated, pressurized hot melt, melt toner to the print paper, after immersion in the final output is the printed text or image.
Laser printers work process control devices and components required for the composition, design structure, control methods and components used in a result of different brands and models have differences, such as:
¢Ù The photosensitive drum charging different polarity.
¢Ú photosensitive drum parts used in a different charge. Some models use the wire electrode discharge drum way to recharge, and some models use rechargeable rubber roller (FCR) of the photosensitive drum to recharge.
¢Û high-pressure transfer components used are different.
¢Ü photosensitive drum to light a different form. Some models use the scanning mirror directly on the photosensitive drum scanning exposure, and some models use the scanning laser beam after reflection on the photosensitive drum to light.
However, they work essentially the same principle. By the laser emits a laser beam through the mirror of Objects Launched into acousto-optic deflection modulator, at the same time, sent by the computer graphic dot-matrix binary information sent from the interface, font generator, forming a binary pulse shape required to information, the signals generated by the synchronizer control of nine high-frequency oscillator, and then by the frequency synthesizer and power amplifier is increased to acousto-optic modulator on the right by the mirror of the laser beam modulated injection. Modulated beam injection multi-faceted rotating mirror, and then through the wide-angle focusing mirror to focus the beam after the shooting to the photoconductive drum (cartridge) surface, so that the angular velocity scan into a line speed scanning, complete the scanning process.
Cartridge surface first be charging a very charge, so that it can obtain a certain potential, followed by the graphic image of the information contained in the laser beam exposure, then the cartridge electrostatic latent image formed on the surface, after a magnetic brush imaging device imaging, latent image that is into a visible toner image, after a transfer zone, in the transfer electrodes of the electric field, the toner will transfer to an ordinary piece of paper and finally through the warm-rolled plates and high-temperature thermal fixing, that is, melting a piece of paper condensate out the text and images. Graphic information in print before the cleaning roller to remove toner does not transfer to go, elimination of residual charge on the lights to drum clearance, and then by the system for thorough cleaning of paper cleaning, you can enter a new one work cycle.
History
Laser printers are Xerox's invention of the late 60's, using the electronic camera (Electro-photo-graphy) technology. The technology uses a laser beam scanning optical drum, by controlling the laser beam to pass off the opening with the suction drum and non-smoking toner, the light absorption of the toner drum then transfer to paper to form print the results. Laser printer controller, the entire printing process can be divided into stages of processing, ink film and the transfer phase.
With the stylus printers and inkjet printers than laser printers have very obvious advantages. (1) high density. Laser printers print a minimum resolution of 300dpi, there is 400dpi, 600dpi, 800dpi, 1200dpi and 2400dpi and 4800dpi resolution and so on. (2) high speed. Laser printer print speeds as low as 4ppm, typically 12ppm, 16ppm, some laser printers print at speeds up to 24ppm and above. (3) low noise. Typically 53dB less than ideal for use in a quiet office space. (4) handling ability. Laser printer controller has CPU, a memory, the controller is equivalent to the computer's motherboard, so it can be a complex word processing, image processing, graphics processing, which is stylus printer and inkjet printer can not be completed, and it is page printers and line printer differences.
What is laser printer how to print great-looking text and graphics for? In fact, laser printers and copiers in the print process basically the same. The difference is that for the laser printer, the images in print before the action took place had been created. First of all, the need to print the contents of the computer into the computer read it to understand the code, and then provide the code sent to the printer. At this time, the printer language then decipher the code into a lattice pattern - the deciphering process is very important. Excellent printer language created bitmap-like pattern on the screen and displays exactly the same, this consistency is the laser printer has been pursuing a "WYSIWYG (What You See Is What You Get)". After deciphering the bitmap sample was sent to laser generator, laser pattern generator according to the content quickly to open and shut in response to the laser beam onto a rotating drum through charge on the drum surface by laser irradiation to the whatever Local charges have been released out, while those who do not shine on laser is still a place with a charge.
For example, if the printer language generated by the bitmap, only in the third row at the third column there is a dot, and the rest are blank, so laser generator will be issued only in this location a bunch of laser irradiation to the induction drum and the remaining positions of laser generator maintained off state. Then induction is only the third line of the surface of the drums at the third column of that point without charge, while the rest remains the state of charge, when laser printers handled in two ways: 1. Only to this point color, The remaining part of the non-color (white produces black spots); 2. only for the rest of color, on this point does not color (to produce black white points). The first approach is called "write black", the second approach is called "write white." Obviously, if in this case, we want to print out a way to write a white-black spots, then we must be allowed to shine everywhere, laser sensors outside the drum surface, except for this point all the position (note that the role of the laser is just discharge, rather than the charge ), in other words, the point is to ensure that only live, and the rest of the charge have been released out of laser. In this case, because the laser beam to shine everywhere except for this point all but the area and therefore take quite some time before the printer to print out this little black spots. In most environments, the printer part of the actual need to print a maximum of only one-third of the entire page, so most of today's laser printers are used to write the way black printing, this can shorten the laser scanning time.
Work process 1
Of course, the laser printer is not only the entire printing process including laser generator and a sensor drums, there are many other components are also involved in the print job.
(1) printer controller: printer controller is responsible for receiving the print data transmitted from the host, and these data into images. The printer controller to deal with a lot of procedures, including communications with the host to explain the host print command, formatted print content (that is, ready to create the image, including setting the paper size, side page, select the font, etc.), raster-based (create a dot matrix image ), and finally the image sent to the print engine. A different printer language on the controller to issue different commands, different manufacturers also use different methods to design their own printer controller.
(2) Printing devices: a set of print device is a combination of electronic and mechanical systems, which can generate a dot-matrix printer controller, graphics print them out. Printing device has its own processor to control the engine and the circuit. In general, printing device consists of the following components constitute a: laser scanning device, sensing drum, toner cartridges, imaging devices, static rollers, adhesive devices, the paper transfer unit, cleaning blade, a paper feeder and tray.
Laser-scanning device is sometimes referred to as "raster output scanner (ROS)", includes a laser generator, rotating mirror and a lens. Generator, the laser projection laser drum surface in the induction of all of the points need to print, and in print where you do not need to remain closed (write white printer is just the opposite). Laser generator itself is fixed, the laser beam through a rotating mirror to achieve the laser sensing lateral movement of the drum surface. Laser generator and rotating mirror must be designed to be extremely precise in order to ensure that they synchronize their work, laser-accurate projection point to the correct position. Laser sensor drum surface, the longitudinal movement by sensing the rotation of drum itself to achieve.
Induction Drum, also known as "by the optical device," or directly referred to as "Drum." Induction was cylindrical drum is usually the surface is extremely smooth. Its surface may be electrostatic charge, electrostatic encounter a light will be released out. In contact with the laser before the drum surface is uniformly charged electrostatic drum, when the laser beam projected onto the surface of the drum a certain point, this point will be released out of the static, so that the surface of the drum will produce a non-charged point. Drum with a relatively slow but constant rate of absolute rotation, the laser can be continuously formed on the surface in the dark, with no gaps vertical projection. This rotating mirror drum for sensing lateral movement and vertical movement of the laser in the dark on the surface, "write" out of an often unseen, non-static images.
Toner cartridge is used for holding the device. Some of the printer cartridge and drum fitted with sensors, known as the "Print component." Toner is special in many synthetic plastics charcoal, iron oxide produced. Toner raw materials are mixed, melted and re-solidification, and then crushed into tiny particles the size of the same. Toner more subtle, more homogeneous, the resulting images more detailed. In all types of toner, the HP's Microfine toner particles smaller than other brands of particles 20% to 50%, and therefore enjoys a high reputation in the industry.
Work process 2
Imaging device is actually a roller covered with magnetic particles. These magnetic particles attached to the roller surface, like a very fine "brush." This roller drum and toner sensor respectively close together, when the roller rolling, the roller surface of the cartridge, where small particles start with, "Brush" to a uniform layer of toner, and then the toner, after Induction drums when they are adsorbed to the induction drum surface. Write black printer's imaging device has the function of the toner charging, because If you want to make toner only be sensitive drum surface with a static part (that is, laser-scanned point position) of adsorption, must be made of carbon powder with a charge (for a write white printer, this process is completely the opposite). At this time the surface adsorption of the toner drum, they formed a very clear image, the next step is to transfer this image to the paper.
Paper conveyor transfer device is a laser printer paper, the most important mechanical devices. This device by two motor-driven roller to achieve the delivery of the paper. Paper by the feeder, through the induction drum, heating roller and other components, and finally was sent the printer. Laser printers in the rolling equipment, such as photosensitive drums, magnetic roller and feed roller rotation must be carried out simultaneously, and they must maintain a consistent pace in order to ensure accurate printout. In general, these are based on feed roller device as the center, through the gears meshing with each other to achieve the same speed rotation.
Bonding device through the transmission device through the induction of paper drum, the drum surface of the toner attached was again adsorbed onto the surface of paper, when the surface of paper while the image formed by the toner, but the toner to the paper, the adsorption force and is not very strong, slightly stronger wind that can blow those away from the paper surface of toner. To make toner permanently attached to the paper surface to be bonded to the toner to deal with. We know that the toner raw materials are synthetic plastic charcoal, this material may be melted at high temperatures. Toner re-solidification after melting, it can permanently glued to the paper surface, in the laser printers within the two close together, very hot rollers, their role is right between them through the paper from the heat, to toner melt adhesion to the surface of the paper. The heating of the paper out of the final output to the printer's paper tray, when the entire printing process to an end.
