We usually luminous objects known as the light source, such as the sun, lights, burning candles and so on. Light has energy, it can make objects heat, so that sensitive photographic film, and this is the phenomenon of energy conversion. Including in the beam of light, the light beam into the eye, it caused people's vision, so we can see the launch of the light source. So why do we also see non-luminous objects do? Is because the light source to launch light reach them, do not light-emitting objects by light, to the diffuse reflectance of light in all directions into our eyes, so we can see non-luminous object.
Have a laser light source, and is obviously different from ordinary light sources. Ordinary incandescent light sources, such as through the current heating tungsten atoms to the excited state, the atoms in the excited state spontaneous constantly emitting radiation. This common source of great and diffuse scattering, and can not control the formation of focused beam, it can not be used for laser printers. Laser printer required laser beam must have the following characteristics:
¢Ù high directivity. Issued by a certain distance from the beam does not scatter and diffuse.
¢Ú high monochrome nature. White light by the seven-color optical components.
¢Û high-brightness and is conducive to a concentrated beam with high energy physics.
¢Ü high coherence, easy stacking and separation. Laser is the laser scanning system light source, with a directional well, monochrome strong, coherent and high-energy concentration, easy modulation and deflection characteristics. Early production of laser printers use helium - neon (He-Ne) gas laser, the wavelength of 632.8μm, characterized by a higher power output, size of which is long-lived (typically more than 10,000 hours) and reliable performance, low noise and large output power. But because the volume is too large has now basically eliminated. Modern laser printers are using semiconductor lasers, often gallium arsenic - aluminum gallium arsenic (CaAs-CaAlAs) series, which emits a laser beam of near-infrared wavelength is generally light (λ = 780μm), the cartridge with the photosensitive wavelength sensitivity characteristics match. Semiconductor lasers small size, low cost, direct internal modem is a portable light source desktop laser printers.
Laser scanning is used to generate a very small spot of high precision for high-quality text and graphics printing, commonly used in laser scanning system working principle is: the material in the workplace settings at both ends of two parallel mirrors (gate ), which between the two mirrors form a resonant cavity. Cavity mirrors for a total reflection mirror, another piece of mirror for a half, when it is stimulated material, atomic spontaneous emission of photons in the resonant cavity back and forth constantly reflection of the photon radiation is increasing. When superimposed photon resonant cavity to a certain amount, it will penetrate the semi-reflective mirrors to issue a bunch of very strong light, this is the laser. This issue is very concentrated beam of light, almost no scattering, as long as we make use of wavelength control technology will be controlled at 700 ~ 900μm (nm), it generated by the laser on a laser printer to meet the photosensitive drum exposure needs.
Used in modern semiconductor lasers, laser diodes used, its principle and is very similar to an ordinary diode, such as have a pair of PN junction, when the voltage and current when added to the laser diode, P-type semiconductor material in the hole and the N-type materials have relative movement of free electrons, PN junction Department carrier density increase is very large, free-electron and hole re-composite, resulting in stimulated emission, releasing characteristics with laser photon, resonant cavity by laser reflection mirror-reflection, through the laser hole and hole focusing mirror, shoot a laser beam.
Generated from the laser can be seen, a laser beam covers only one of the main wavelength of light, it is monochrome. Every light in one direction along the spread of mutual superposition combination, we referred to as "coherence." The characteristics of the laser beam to a fine reach a target, and almost no scattering. Each bore in like a laser beam injection of bullets, each bullet hit the target only a hole. To play a "one" word, we should shoot a lot of bullets, along the "one" in the direction of making a lot of holes, the formation of a "one" with the word horizontal point, this is what we call the "dot-matrix array," is back to say "dot-matrix image" technology base.
Graphic information on laser printers, also supported by the dot-matrix composition. The higher print quality requirements, the formation of a dot-matrix characters are also more. Laser scanning the lattice formation of four methods. Single-scan: The characters in each line of his party's lattice information, sent to the scanner in the scan, known as single-scan. Multi-line scan deflection order: high-frequency signal generator in turn have nine different frequencies, according to the principle of Bragg diffraction, they deflection modulator will have nine different deflection angle of the scan lines, and then switch to a tiny mirror rotation angle, scan out of the lattice from left to right information. As a result of this method will probably only turned a tiny mirror to the point of view, it is equivalent to one-way scanning method of 1 / 132, can form a word, it is also known as small raster scan. At the same time, multi-line deflection scan: refers to high-frequency drive circuit at the same time produce nine different frequencies, the post-synthesis to the deflection modulator. At the same time, numerous multi-line deflection Scanning: This method and multi-line scan at the same time the deflection is the same category, but from the formation of a character differ. In scanning the high-character dot-matrix, a complete character is divided into several times of the scan is complete. Graphic information on the formation and character dot-matrix dot-matrix is basically similar to the formation.