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How is LED technology better than laser technology? (and what is worse)

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How is LED technology better than laser technology? (and what is worse)
Terminology
Laser printing is a common name for a printing method that uses the principle of dry electrostatic transfer. The essence of the principle is that the coloring substance (toner) “sticks” electrostatically to the light-sensitive drum where it has been exposed to a light source. The toner is then electrostatically pulled onto the paper, resulting in an image on the paper which is fixed in the printer’s furnace by temperature and pressure.
Traditionally, a single laser diode is used as the light source, the beam from which, passing through a scanning system, hits a light-sensitive drum. But the laser diode is not the only light source used in modern printers. A worthy and in many ways interesting alternative to the laser are light emitting diodes (LEDs from Light Emitting Diode) assembled in a ruler and called the LED Ruler. Both light sources allow you to produce prints absolutely identical in terms of the set of consumer properties. However, each technology has its own characteristics.
Let’s take a closer look at LED printing.
Main advantages :
Compact and no moving parts
no ozone emission
high picture accuracy
information security
high-speed performance
How is LED technology better than laser technology? (and what is worse)
Laser (top, cover removed) and LED (bottom) light sources for electrographic printers
How is LED technology better than laser technology? (and what is worse)
LED strip design : top to bottom – cover with focusing lenses, textolite board with LEDs and contact group, dielectric and metal housing
How is LED technology better than laser technology? (and what is worse)
Individual LEDs at high magnification (600dpi LED bar)
Compact and no moving parts
The light source in a LED printer is thousands (from 2, 500 to 10, 000 pieces) of individual LEDs mounted on a textolite board in the same way as conventional electronic components of modern devices are mounted. The textolite board itself is placed in a metal case to prevent damage.
Because of the miniature size of the LEDs, they can be housed in a very small device called an LED strip (also called a printhead). The size of this head is so small that OKI LED page printers are still the most compact black and white printing devices in the world!
A laser printer, on the other hand, uses a rather complicated optical-mechanical system which has finely tuned mirrors and a rotating multi-sided prism (which makes a slight whistling noise when the laser printer is in operation). Traditionally, a system with moving parts is said to be less reliable than one without. This tenet has also been proven over time in the case of OKI LED heads. Since 1999 they have had a lifetime manufacturer’s warranty!
How is LED technology better than laser technology? (and what is worse)
No ozone emission
Ozone is triatomic oxygen, which is a highly reactive chemical element (oxidizer). In small amounts ozone is useful for the human body, but in large amounts it is very harmful, because it is a conditionally potent poison.
One of the common sources of ozone in the home is copying and copying machines. Such equipment used to have an element called a coronator, which is a thin wire through which a high voltage current flows. The oxygen in the air in contact with this wire is ionized and ozone is produced from it.
In modern devices, the coronator has been abandoned, replaced by a special roller, which actually prevents the release of ozone. But in laser printers, another source of ozone remains: the laser beam itself. If you look at a diagram of a laser printing system, you see that the laser beam makes a fairly long journey through a system of mirrors and lenses before it reaches the surface of the image drum. Along the way it electrifies the air which also produces ozone. Not as much as the coronator produced, of course, but you can still smell the ozone when the laser printer is in operation.
LED printers are completely devoid of this disadvantage. The distance from the LEDs of the print line to the surface of the image drum is so small that there is almost nothing to ionize in this gap, and the characteristics of the light emitted by the LED lines are such that they cannot decompose oxygen with the release of ozone. This is why LED printers are the most environmentally friendly devices of modern toner printing.
High fidelity image
How is LED technology better than laser technology? (and what is worse)
In a laser printer, each line of the future image is formed by “scanning” the surface of the light-sensitive drum (photodrum) with a laser beam. The beam deflecting prism is rotated by means of a stepper motor. At each step the prism is rotated by the same angle. However, due to the fact that in order to reach the surface of the drum, the beam needs to pass differently in the center of the drum and at its edges, the distance between neighboring points will be different. In addition, due to the fact that the beam falls on the edge of the drum at an angle to its surface, the very shape of the dot to be formed on the photodrum will not be circular but oval.
In an LED printing system, there is a different LED above each dot of the image drum. The distances between the diodes in the line are the same, and the shape of the dot does not change along the length of the photodrum. It is these features that ensure the same high image accuracy both in the middle of the sheet and at the edges. And that is why professional printing systems do not use a laser scanning system, but rather work on principles similar to those used in LED printers.
The differences in accuracy described above can be seen when you strongly magnify the fine text. For example, below are two 1.5 pt text fragments made with laser and LED printers and scanned with the same parameters:
How is LED technology better than laser technology? (and what is worse)
A print made by a laser printer at 1200x1200dpi. Note the quality of the small elements of the letters – all the “circles” are filled with toner.
How is LED technology better than laser technology? (and what is worse)
A print made with a 1200x600dpi LED printer. Even though the physical resolution is initially lower, the LED printer does a much better job with small text details.
Information Security.
A laser diode, which works as a light source in a laser printer, emits a series of successive light pulses which reach the surface of the image drum, creating an electrostatic image on it which is then translated into a print. However, like any other electronic device a laser diode emits not only in its working range (laser beam) but also in the radio range, being in fact a radio transmitter. Each dot that is placed on the paper, and from which the printed image is produced, corresponds to one pulse in the radio spectrum. Using modern technology, these pulses can be received at the radio antenna, sent to the computer, and used to reconstruct the printer’s printable image.
Light-emitting diodes in the LED printer also create electromagnetic oscillations, which can be captured by a receiver, but due to the fact that the LEDs in the printing line is a lot, and they all flash simultaneously, the air goes “white noise”, which can not be deciphered (to determine which of the diodes “flashed” and which – no, respectively, where it was put on paper point and where not), that is impossible to restore the image that is printed on a LED printer. Such protection of documents printed on LED printers may be in demand in any sensitive places when printing classified and classified information, as well as where printed personal information about customers. After all, according to the law on the protection of personal data, no matter how the data was leaked, the responsibility under the law is always the same. So if you intend to print personal data on a laser printer be prepared for the fact that you will be guilty of violating this law. So it is better to use LED printers to print such data right away!
How is LED technology better than laser technology? (and what is worse)
High working speed
Because all the LEDs in the line are placed in a single row and flash at the same time, the printing speed of LED printers is virtually limitless. In contrast, laser printers, which have to draw each line of the image sequentially, have physical limitations on the maximum print speed depending on the horizontal resolution used, at which there is no geometric distortion of the printed lines. The graph to the right clearly shows that at a physical resolution of 1200dpi, the maximum print speed of a laser printer is about 20 pages per minute. At higher print speeds, there will be line distortion in the lines of the print: the lines will not be perfectly horizontal, but slightly slanted. The alternative to distortion is to reduce the physical resolution. For example, when printing at 600dpi, laser printers can reach a maximum speed of 50 ppm. If high speed at high resolution is to be achieved, laser printers are forced to have two or more laser engines, each of which will only handle a portion of the image. This makes the design much more expensive and larger, and creates obvious problems with the setup of such printers. All these problems are fundamentally absent in LED printers, for which the restrictions on printing speeds are far beyond the realistic print speeds that are in demand.
Frequently Highlighted Deficiencies :

Resolution is no more than 600 dpi, and the images produced by LED printers often came out with blurry and fuzzy edges, fine halftone lines had gaps, color matching in color images was inaccurate. Print quality, especially with regard to resolution and consistency, was a weakness of the LED printers.

First, a big misconception about the “no more than 600dpi” resolution. Already in 2000, OKI released two senior models of color printers – C7400 and C9400, A4 and A3 formats respectively, whose resolution of LED liners was 1200dpi. Then came the C7500 (A4) and C9500 (A3), then the C9800 (A3) and finally today’s C9850 A3 format. They all had 1, 200 individual LEDs per inch of LED strip, so that the physical resolution of 1200x1200dpi was achieved.
“Blurry and fuzzy edges” is really a figment of the imagination and speculation. For a very long time in the LED printers used technology smoothing vector images based on the ability of LED rulers to create dots of different sizes. Even the most inexpensive and frankly not the best representatives of OKIPAGE family of black and white printers, gave more than sufficient smoothness of text and vector images already at the basic resolution of 300dpi! Never mind today’s 600 and 1200 dpi printers, which make full use of the same technology!
And the lack of image stability is a serum truth. But… 10 years ago. Indeed 10 years ago the LEDs in the liners were slightly different in intensity from each other, which gave a slight streakiness along the movement of the sheet. But with the advent of the C7000 and C9000 series printers in the year 2000, new rulers appeared where each LED was automatically controlled and normalized to the same level. Since then, issues of image stability due to the difference in LED glow have not been raised again.
Conclusions
Compact and no moving parts
Ensures small dimensions of the mechanism and long trouble-free operation of the unit. The most critical element, the LED ruler, comes with a lifetime manufacturer’s warranty!
no ozone emission
LED technology printers are the greenest of today’s toner printing devices, preventing detrimental effects of ozone exposure such as dizziness and drowsiness.
high picture accuracy
Created documents are characterized by high accuracy and linearity of the image, technologically unattainable by classical laser printers.
information security
LED printers can be used in applications that require increased confidentiality of documents.
high-speed performance
LED printers don’t have to sacrifice speed or print quality because the parallel, full-width illumination gives you the ability to print at any optical resolution without any speed limit, which is unavailable with laser printers.
Which does not apply to LED technology, but is attributed to
Very often when people look at LED printers they wonder what happens if one LED burns out, like a pixel on a monitor screen burns out. But this rather funny question can by no means be attributed to LED technology. The association has to be sought in another field of computer technology and ask the question – what happens if one transistor on the processor burns out? After all, there are orders of magnitude more of them than there are LEDs in the line, and the manufacture of both, by and large, is done using similar technological processes. And in both cases, the weakest link is rejected at the production stage and as a very small percentage of processors with burnt out transistors, and almost do not get into the printer and the LED line with burnt out diodes. If anything happens to the LED strip, it is a failure of the control board, which is responsible for an entire section of LEDs. Individual LEDs in operation fail so rarely that they do not even fall into the statistics of failures, that is outside the 0.01% of total failures of LED printers. And in any case, no matter what happened to the LED bar, we can always be sure that it will be replaced within the lifetime warranty! By the way: LEDs work with an intensity of at least 5000 times lower than laser. That is why they do not break down. That’s why there is such a warranty.
OKI has been developing and improving the LED technology it created since 1987. Today, OKI is one of the few companies that continues to conduct fundamental technological research and independent development in the field of black and white and color printing, investing heavily in it. In this article I have only indirectly outlined areas of development to improve LED technology, but as you can see, in recent years the technology has gotten rid of almost all of its shortcomings.
Sergey Lebedev OKI Marketing Director

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