Working of Laser Printer

A laser printer makes use of a beam of light for printing. This light of the laser changes the electrical charge on the drum, wherever it hits because as the paper passes through the printer, the laser beam strikes at the surface of the drum and this is known as a photo receptor. By changing the charge on the drum, the laser beam can print patterns onto the photo receptor. Once the design created on the drum, it coated with toner from a toner cartridge. In most of the cartridges, the toner is black, but the laser printers are also colored.

Laser printers work by laying down an array of tiny, evenly spaced dots of “ink” on the paper. The dots are so small, and they blend so seamlessly that text looks very nearly as clean as what you get from a traditional typesetting machine. Yes, there are little-jagged edges along curved lines, but they’re hard to see. Graphics sometimes don’t turn out quite as sharp, but they still are bright enough for a professional look in many situations.

The quality you get from your laser printer depends mostly on the resolution, the fineness of the dots it uses to print the images. Resolution measured in dots per inch (dpi), which is how many dots it can write a long with a line, either vertically or horizontally. Most laser printers have had 300 dpi resolutions, but 600 dpi is just now becoming the new standard. If you’re shopping for a new printer and are willing to spend around $2,000, make sure you buy a 600 dpi machine-it’s tough to see any jagged edges.

Although the output of a laser printer sometimes described as “near-type set quality,” don’t mistake the mechanical resolution with the aesthetic quality of good typography. No matter how high the resolution, if you still use typewriter conventions (such as two spaces after periods, straight quote marks [” instead of” and “] two hyphens instead of a dash, underlines, and other typographic faux pas), the text will never really look “typeset quality,” even if you use 2540 dpi. If you are still using typewriter conventions and trying to produce high-quality output, you should check out the books The Mac is not a typewriter or The PC is not a typewriter.

Behind the scenes: a laser printer relies on a process something like that used to generate images on a television. In a TV set, a beam of electrons rapidly scans across the video tube, building a picture out of tiny dots of light. In a laser printer, a tightly focused laser beam does the scanning. Although the laser source itself is stationary, a rapidly spinning mirror directs the laser beam so that it quickly traces a narrow, precisely horizontal line from one side of a different light-sensitive drum to the other. Initially, this drum carries a uniform static charge. As the laser beam moves across the drum, however, it flashes on and off, and wherever it touches the drum, it reverses the static charge of a minute dot.

When the beam reaches the far edge of the drum, the drum rotates precisely. The laser beam then scans back across the drum, continuing to flash on and off. This cycle repeats itself until the laser has etched the drum with a pattern of charged dots corresponding to the entire page to print.

Even before the laser beam has finished its work, the drum’s slow rotation brings the portions already etched into contact with the toner, a black plastic powder that serves as the printer’s ink. The toner itself charged so that it sticks to the dots etched by the laser. Eventually, all the etched areas of the entire drum receive a coating of toner. Meanwhile, a sheet of paper has been drawn into the printer by a system of rollers. In the process, these rollers have given the paper a static charge of its own, but one stronger than the charge on the drum. As the drum presses against the paper, the paper’s charge attracts the toner away from the drum and onto the paper. More rollers move the paper into the fusing system, where heat and pressure affix the toner permanently to the paper. That’s why the paper feels a little warm when it emerges a few moments later from the printer. As this is going on, a thin corona wire restores the drum’s original homogeneous charge, readying it for the next page.

The steps of printing on a laser printer are as follows:

• Cleaning: The process of cleaning will remove the already saved image information and toner from the drum.

• Conditioning: The corona wire will apply a uniform, and a positive charge to the drum and the positively charged toner will cling to the area of the drum that is negatively charged by the laser.

• Writing: When the paper passes through the printer, the drum is given a strong negative charge, which allows the toner to transfer and stick to the paper. The result of this printing is that a clean copy of the image written on the paper displayed in front of you.

• Developing: The toner in the ink cartridge contains a positive charge so that it will be attracted to the drum which is given a negative charge by the laser.

• Transfer: The toner of the drum is transferred to the paper by either a positively charged field or by a transfer roller.

• Fusing: Heat and pressure applied to the paper. The toner melts onto the paper,and the image printed.

Advantages of laser printer

• Laser printers are faster than inkjet printers as their printing speed is fast.

• The replacement of toner is cheaper in the laser printers.

• Laser printers are noiseless.

• Laser printers are efficient.

• Laser printers are highly optimized.

• Laser printers are user-friendly.

Disadvantages of laser printer

• Laser printers are costly.

• Since laser printers are non-impact printers, so they cannot perform double printing simultaneously.

• Laser printers are not economical.

• Laser printers make use of complicated technology. Thus, a large hardware gadget is required, which requires a lot of space.

• Laser printers are also known to be dangerous for health and the environment as it generates ozone which depletes the ozone layer.