Have you ever wondered how a laser beam, in Laser Printers, puts text or images on a paper? We will learn about this interesting printing technology in this article.
Laser Printing is based on the principle of static electricity, the electrical charge built up on an insulated body. Two objects with opposite static electric charge attract each other. A laser printer uses this phenomenon as some type of “temporary glue”. The basic components of a laser printer include a photo-receptor, which is a rotating cylinder or drum made out of highly photo-conductive material.
In the beginning, a wire (called the charge corona wire) with electric current running through it imparts a positive charge to the drum. Some of the Printer and Printers also use a charged roller instead of a corona wire. A laser beam then hits the surface of the rolling drum and discharges certain points. This is how it draws the letters and images to be printed as a pattern of electrical charges.
After the end of this process of setting the charge pattern on the drum, it is coated with the positively charged toner powder. This powder, owing to the positive charge on it, clings to the discharged part of the drum and not on the rest of the drum (positively charged).
The desired pattern is thus affixed on the drum. Now, it is the task for the Printer and Printers to prepare the paper. The transfer corona wire imparts a negative charge on the paper before the latter rolls under the drum. This negative charge is greater than the one on the laser-hit points of the drum, and hence the positively charged toner powder clinging to the drum adheres to the paper. Since, the paper and the drum move at the same speed, the pattern of the image on the drum is precisely transferred onto the paper. The detach corona wire then immediately discharges the negative charge on the paper, so that the paper is separated from the positively charged drum.
Did you see, how your Laser Printer does so much in such a small timespan?