Why can a printer print out words and images? What is the principle!

The working principle of the stylus printer The code sent by the host computer is processed by the printer input interface circuit and then sent to the main control circuit of the printer. Under the control of the control program, the code of characters or graphics is generated, and the print head is driven to print a column of dot matrix graphics. At the same time, the carriage moves horizontally to generate column spacing or word spacing, and then the next column is printed, and the printing is performed column by column. After printing a line, start the paper feeding mechanism to feed paper to generate line spacing, and at the same time, the print head returns to a new line to print the next line; Repeat the above process until printing is completed.

The name of the stylus printer comes from the structure of its print head. The structure of print head is complex, which can be roughly divided into printing needle, driving coil, positioner, excitation disk and so on. Basically, the working flow of the print head is as follows: when the print head obtains the current pulse from the driving circuit, the driving coil of the electromagnet generates a magnetic field to attract the armature of the printing needle, which drives the printing needle to hit the ribbon and print a dot matrix pattern on the printing paper. Because the printing needle directly performs the printing function, this printer is called a stylus printer.

The working principle of inkjet printer is similar to that of stylus printer, and the essential difference between them lies in the structure of print head. The print head of an inkjet printer consists of hundreds of ink channels with extremely small diameters (about several microns). The number of these channels, that is, the number of spray holes of the inkjet printer, directly determines the printing accuracy of the inkjet printer. An execution unit capable of generating vibration or heat is attached in each channel. When the control circuit of the print head receives the driving signal, these execution units are driven to vibrate, and the ink in the channel is squeezed and ejected; Or generate high temperature to heat the ink in the channel, generate bubbles, and eject the ink from the nozzle; The ejected ink reaches the printing paper, and the printing paper produces graphics! This is the basic principle of piezoelectric and bubble inkjet print heads. The control principle and working form of inkjet printer are basically similar to those of stylus printer, so I won't go into details here!

Working principle of laser printer When the host sends data to the printer, the printer first temporarily stores the received data in the cache. After receiving the complete data, it is sent to the processor of the printer, which organizes the data into a signal stream that can drive the print engine. For a laser printer, this signal stream is a set of pulse signals that drive the laser head to work.

The core skill of laser printer is the so-called electronic imaging skill, which combines the principles and skills of imaging and electronics to generate images. The core component is photosensitive selenium drum. The laser emitted by the laser emitter shines on the prism-shaped reflector. With the rotation of the reflector, the light sweeps from one end of the drum to the other end in turn (there are various focusing lenses in the middle, which makes the spot scanned on the surface of the drum extremely small). The toner cartridge rotates in steps of 1/300 inches or 1/600 inches, and scans on the next line. The selenium drum is a cylinder coated with organic material, which is charged in advance. When there is light irradiation, the resistance of the irradiated part will change. The data signal sent by the computer controls the laser emission. The light scanned on the surface of the toner cartridge is constantly changing. Some places are irradiated, the resistance becomes smaller and the charge dissipates. Others don't have lights, but there are still charges. Finally, a latent image composed of charges is formed on the surface of the toner box.

Toner is a kind of tiny plastic particles with charge, and its charge is opposite to that on the surface of toner box. When the charged toner box surface passes through the developing roller, the charged part absorbs toner particles, and the latent image becomes a real image. When the drum rotates, another transmission system feeds printing paper through a set of electrodes. The printing paper has similar polarity, but it is much stronger than the surface of the drum. Then the paper passes through the toner drum with toner, and the toner on the surface of the toner drum is attracted to the printing paper to form an image on the surface of the paper. At this time, the toner and the printer are combined only by the attraction of electric charges. Before the printing paper is sent out of the printer, it is heated at high temperature, and the plastic toner melts and is fixed on the surface of the paper during the cooling process.

After the toner is transferred to the printing paper, the surface of the toner drum continues to rotate, and the remaining toner is removed by the cleaner, thus entering the next printing cycle.

According to the above principles, we can see that the essential difference between laser printers and needle printers or inkjet printers lies in

The laser printer prints a whole page at a time, page by page; However, both stylus printers and inkjet printers print one line at a time instead of one line at a time. Therefore, under similar printing requirements, the printing speed of laser printers is faster than that of needle printers and inkjet printers, which is also an advantage of laser printers.