12/29/2007
Briefly, LED (Light Emmitting Diode) technology allows for
- smaller and more reliable printing devices
- no ozone when printing
- higher imaging precision
- information security
To give it a detailed explanaition, I first need to tell what laser printing technology is.
Laser printing is a common name for printing using method of dry electrostatic transfer. This method intents that toner sticks to photosensitive drum in areas affected by light. Then toner is transferred to paper forming an image that is afterwards cured by pressure and heat. And it is electrostatics that actually transfers the toner to drum and from drum onto paper.
Traditionally, they used laser as a source of the light, but modern printers have an alternative – Light Emitting Diodes. Both light sources allow producing prints identical from customer point of view, but also have their peculiarities.
What are the advantages of LED printing technology?
1. Space effectiveness and absence of moving parts
Light source in LED printer is made up to thousands (2 500 to 10 000 pieces) of light emitting diodes assembled on printed circuit board just like most modern electronic components are done.
Since light emitting diodes are very tiny in size, they can be placed very densely in a LED printhead. Meanwhile, laser printers utilize a complex precision system of mirrors and a multifaceted prism (the one that makes hissing noises when printing). And it is generally acknowledged that the system with moving parts is less reliable than the one without such parts.
2. No ozone is produced
Ozone is very active chemical element that is useful for humans in small doses and hazardous if overdosed.
One of the household sources of ozone is printers and photocopiers. Previously these devices had corona wire, a wire that conducted high-voltage current. Contacting with this wire, the air got ionized and turned into ozone.
In modern printing and copying devices corona wire was replaced with a special roller and that spotted ozone emission. However, laser printers still have a source of ozone, it’s the laser beam. The beam goes a long way through mirrors and lens until it reaches the drum surface. On its way the beam electrifies the air and produce ozone, but truth be told, in smaller amounts than the corona wire.
The LED printer doesn’t have this drawback. The distance between LEDs of the printhead and the photodrum is so short there’s nothing to ionize. That is why LED printers are most environment friendly devices printing with toner.
3. Higher imaging precision
To explain this point, I’ll give some give technical background.
In the laser printer, the laser beam forms a line of image by running over the surface of photodrum. To reach the center of the surface and its edges, the laser beam has to cover shorter and longer ways respectively. Hence, the distance between adjacent dots is different. Besides, the beam lights upon the photodrum at an angle, which makes the dot not round but rather oval.
In the LED printer, there is a “personal” light emitting diode over every dot on the surface of the drum. Distances between diodes in the LED printhead are identical, and dots’ shape stays the same along the drum length. These characteristics provide high imaging precision in and center and ta the edges of a sheet.
Honestly speaking, this difference is only noticeable when printing fine details, like microprint.
4. Information security
The laser diode used in laser printers emits a sequence of light impulses which create an electrostatic image of the drum. Just like any other electronic device, laser diode emission is not limited too infrared radiation. It also produces radio signals, hence, working as a radio transmitter. Under modern level of technical development, these signals can be intercepted thus making it possible to restore what was printed of laser printer.
Just like is case of laser printers, devices build on LED technology such radio impulses too. However, due to huge number and simultaneous flashing of diodes in the working printhead, it is impossible to decipher what each diode emitted and to restore the image printed.
Sure, this is only important when you print some confidential or security sensitive documents. Your to-do list would not be of any interest to anyone, or would it?
