How does a so-called "LED monitor" work?

5

Every here and there I hear about new LED monitors. I imagined that they were really LED monitors - that their screens were formed of multiple tiny LEDs that lit up in a controlled manner to form an image. Yet turns out they are LED backlit LCD monitors.

What's the difference between this and a trusty Belinea 10 17 51 I've been using for the five years already?

sharptooth

Posted 2010-06-15T06:16:54.200

Reputation: 831

Note that although "LED monitors" are not what you once imagined them to be, "OLED monitors" are actually exactly that: millions of tiny (organic, hence the "O") LEDs forming subpixels of the screen. Yes, marketing is confusing. – Ruslan – 2019-12-01T10:16:12.590

Answers

13

For a more in-depth explanation:

You got the concept wrong when you imagined it to be millions of LEDs flashing the different hues of colors to give you a display - all these kind of monitors are made of invariably 2 layers - a front layer of LCD (Liquid Crystal Display or Liquid Crystal Diode) that makes up the dots you see as pixels, along with the display of color.

alt text

This LCD layer is then back-lighted using light tubes at the back, giving it brightness. Formerly, LCD displays use to use CCFL (Cold Cathode Flourescent Lamp) as a light source at the back, but however in recent years there has been a marked shift towards the use of LED (Light Emitting Diode) as a back-light source. The advantages of LEDs are as follows:

  1. Faster Turn On: LEDs can reach maximum brightness faster than CCFLs, in fact almost instantly.
  2. More Neutral Colors: CCFLs are known to give a warm/yellowish tint. LEDs have a more neutral whitepoint.
  3. Brighter: LEDs are brighter generally than CCFLs, thus allowing a display to achieve even higher maximum brightness.
  4. Thinner: The reason LEDs are coming into prominence is that it was driven by the notebook sectors - LED back-lighting can be made thinner than CCFL back-lighting.
  5. Longer-Lasting: Apparently, LEDs are rated for more life than CCFLs. Also the degradation over time is less severe than CCFLs.

Well, these are the primary reasons why LED-based LCDs are considered to be better than CCFLs. They still come with a price premium though.

caliban

Posted 2010-06-15T06:16:54.200

Reputation: 18 979

LEDs have a lifetime longer than my house... – RCIX – 2010-06-19T10:21:13.070

LED screens also potentially use less electricity and deeper blacks than CCFL backlit screens. – paradroid – 2010-10-25T07:02:11.400

2

I believe the blacks on an LED screen are blacker too since portions of the backlight can be turned off when black is needed. A normal LCD, tun the crystal opaque to stop the light coming through. No backlight = better black.

\\Greg

uSlackr

Posted 2010-06-15T06:16:54.200

Reputation: 8 755

1

The backlight uses less energy and generates less heat then fluorescent backlights.

Ignacio Vazquez-Abrams

Posted 2010-06-15T06:16:54.200

Reputation: 100 516

Emmm... Do you imply that pre-"LED" monitors had fluorescent backlights? That sounds insane. How can a fluorescent lamp be durable enough? – sharptooth – 2010-06-15T06:33:34.430

O_o Where are you located that has glass which shatters when touched... – Ignacio Vazquez-Abrams – 2010-06-15T06:43:53.543

I see there is irony in your comment but I'm not a native English speaker and just don't get it. Could you please explain what you mean? – sharptooth – 2010-06-15T06:54:04.497

I've seen this too. The back light is a fluorescent light at the bottom of the screen and a special kind of plastic is used to evenly distribute the light to the entire screen. You can see this at the bottom of the page here: http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/

– James T – 2010-06-15T07:00:18.493

@James: I see now. Didn't know they have a special kind of fluorescent lamps suitable for display backlights. – sharptooth – 2010-06-15T07:04:34.860

Asked: 2010-06-15T06:16:54.200

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Active: 2011-08-21T08:52:22.837