LED Printers: The Common Printing Tech You Haven't Heard Of

Today’s video is about printers.

I know, you’re probably filled with excitementat the mere mention of printers, but please remain calm.

If you were to go shopping for a printer, you’ll almost certainly find yourself choosing between an inkjet printer and a laser printer.

Or perhaps a 3D printer, but we’re not talkingabout those today.

Now, I won’t get into the many reasons thatI don’t really like inkjet printers for anything but photo printing because that’snot really the point of this video.

Instead, we’re going to talk about a subsetof the laser printer that seems to fly under the radar.

The LED printer.

Now, if you’ve never heard of this beforeI wouldn’t blame you.

Fundamentally LED printers are the same asa laser printer.

They still use powdered toner rather thanliquid ink.

They use photosensitive drums to transfertoner to paper (along with corona wires and/or other charge inducing or destroying doodads).

And a fuser melts this toner onto the paper, so a tall stack of freshly printed printouts is nice and warm, just asking you to giveit a hug.

But where they differ is in how the imageis drawn on the drum.

And to understand why that’s important, let’s have a quick lesson into how laser printing works and how it came about.

Laser printers are essentially an offshootof the photocopier.

Using a process called xerography, which comesfrom the Greek for dry writing (and now you know where Xerox got its name), analog photocopiersuse a cylindrical drum coated in a photoconductive material.

This material becomes conductive when exposedto light.

To duplicate the image, the drum is firstcharged by a corona wire, which produces a high voltage and gives the drum a static charge.

The now negatively charged drum is rolledunderneath a piece of paper to be copied, where a lens focuses the image of the paperonto the drum, and a bright light source provides illumination.

Because the photoconductive material willconduct electricity when exposed to light, any bright areas become discharged, as a pathto ground can now be completed.

Dark areas, where printing or handwritingexist on the original, will remain negatively charged.

This drum is then rolled against a supplyof powdered toner, which is positively charged.

This toner will thus want to stick to anyareas of the drum that remained negatively charged from the original exposure.

Now the drum has a coating of powdered tonerin the same pattern as the writing or image or whatever in the original document.

Next, another corona wire creates a strongernegative charge in the paper that is to receive the toner, and this stronger charge will attractthe toner off of the of drum and onto the paper.

And finally the paper, now covered in powder, goes through the fuser unit, which melts this powder to the paper, and thus a stable photocopyis made.

Fast forward to the late 1960’s, and GaryStarkweather, an engineer from Xerox’s product division, had the idea of using a laser beamto draw directly onto the imaging drum of a photocopier.

With computer control, you could draw textand images directly on the drum with the laser, thus turning it into a printer.

And that’s exactly what happened.

Using a laser diode, lenses, and a spinningmirror, laser printers draw onto the drum in lines, and the laser is pulsed on and offto create the image.

The resolution of the printer is determinedby the number of lines it can draw in a given unit, in addition to the maximum number oftimes the laser can be pulsed on or off within that line.

Often the resolution is measured in dots perinch, so a printer with 600 dpi will scan the drum 600 times along the length of oneinch, and the laser can pulse on and off 600 times within one inch of each line, meaningeach square inch has 600 by 600 discrete points that can be either on or off–that is, blackor white.

Incidentally, this method of creating an imageusing lines of light is strikingly similar to how analog television works.

I made a series on television if you’d liketo check it out, but the pattern is called a raster.

Raster scanning in laser printers requiresthat the entire image, in its full resolution, be loaded into its memory before printingcan commence, as it has to be done in one shot.

It can’t start and stop like an inkjet printer, particularly because the fuser unit is liable to burn some paper (or at least singe it alitte) if it were to suddenly stop mid-print.

So, laser printing works.

And it works really well! But the actual laser mechanism is kinda big, and relying on a spinning thing to make the image introduces more moving parts and complexity.

And that’s where the LED printer comes in.

When did it come in? And who invented it? I’m not sure.

It’s a weird footnote into the developmentof the laser printer, but Oki claims to have made the world’s first LED printer in 1981.

It’s surprising how little info there seemsto be about LED printers, though as we’ll see, perhaps that’s to be expected.

What makes LED printers different? Well, rather than use a scanning laser, LEDprinters use LEDs.


But in a unique way–this Brother HL-3040CNis a color LED printer.

If I lift on the lid, you’ll see these fourbars here that kinda flip out of the way when the lid’s all the way up.

There are four because this is a color printer–oneeach for cyan, magenta, yellow, and black (more correctly referred to as key).

These bars are the key.

Each of these things is an array of tiny individualLEDs.

Each LED handles one column of pixels–ordots–on the page.

This printer has a resolution of 600 DPI, so along this entire bar there are roughly 5, 000 LEDs.

If you look closely you’ll see a patternof dots–these are lenses that focus the light from multiple LEDs behind them onto the correctspot of the drum.

The LEDs themselves are so small as to benearly invisible to the naked eye.

Below these assemblies lie individual drumand toner cartridges.

You can see that when the lid is closed, theLED bar sits right on top of the drums.

You’ll also find evidence of toner mishaps, but, ehhh.

So when this printer prints, rather than spinninga mirror and pulsing a laser on and off, each LED simply pulses on its own.

As the print drum rotates, the LEDs will flashwhen they need to, and stay dark when they don’t.

There are many times as many light sources–infact thousands of times–compared to a laser printer, but the lack of a mechanical component, plus the direct physical alignment of the LEDs with the drum, means that LED printersmight be more reliable.

And they certainly are more compact.

Particularly with color printers.

Notice how this printer has each color oftoner simply in a row.

Because there’s no need for a complicatedoptical system, this printer is essentially just 4 printers lined up in one case.

And if I pull one of these out, you’ll seehow small the toner and drum cartridges are.

Yes compared to an injket these are laughablybig, but for a toner-based printer this is actually pretty small.

This design also gives color LED printersa huge advantage compared to laser–speed.

To convert from black and white to color, this printer essentially just takes the printer part, then Ctrl-C Ctrl-V’s it a fewtimes.

The paper travels in a straight path as itgets black, yellow, magenta, and finally cyan toners.

Then it’s fused on its way out.

Color LED printers used to boast that theirprinting speeds were nearly the same between color and black and white.

Many color laser printers, such as this onefrom Samsung, print at a fraction of their black and white speeds, because when printingin color, the paper has to take a meandering path through four printing assemblies.

With setups like this from Brother, it’sjust boom boom boom boom, fuse the toner, and we’re done.

Now, laser printers do still have their advantagesover LED.

It’s easier to achieve a higher resolutionwhen you have the benefit of motion, rather than relying on smaller and smaller LEDs.

Plus, apparently LED printers can have lessconsistent images due to slight variations between each LED.

I can’t say whether I’ve noticed thatin person, but this paper from Xerox sure is trying to convince me.

But here’s the kinda humorous bit.

I’m willing to wager that many “laserprinters” available on the market are in fact LED printers, but they’re just notso clearly labeled.

Poking around on Amazon I found plenty ofprinters that don’t have much of a difference between their color and black and white speeds, and some printers like this Canon have the toner arranged suspiciously similarly to thisBrother printer.

And Brother is definitely still using LEDprinting technology, as evidenced by this picture on this Amazon listing.

To their credit, they simply call it a “digitalcolor printer” and it’s Amazon that’s labeling it as “laser printer technology”.

Anyway, maybe this Canon is a real laser printer, and they’re just packaging the laser scanners more efficiently so that the paper can passin a straight line.

But there are still some color laser printerson the market that print fast in black and white and at a leisurely pace for color.

The Samsung unit we looked at earlier printsat a respectable 19 pages per minute black and white, but only 4 ppm color.

Not so “Xpress”, after all.

In any case, I think that it’s a shame howlittle is known about the LED printer.

Sure, on the surface, it’s just a laserprinter.

An LED printer will produce near identicalresults, and behave in a near-identical fashion.

It’s still a drum and toner system–howthe image gets to the drum is arguably trivial.

But I think it’s a clever way to handleit.

Thanks for watching this (for this channelanyway) quick video.

I’ve interrupted the series on the compactdisc to bring you this video and we’ll be resuming where we left off soon.

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Thank you for your consideration, and I’llsee you next time!.

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