the technological differences between LCD and LED displays

posted on February 20th, 2010, 8:48 am

There was recently a off topic debate in the "ideas and requests" section of the forum which was started by borg101 on LCD and LED displays. now from that i can see that many ppl dont know the technological design differences between LCD and LED displays, so i thought that i myself being a Electrical Engineer shall set the record straight.

LCD DISPLAYS
A LCD(liquid crystal display) display works by having a layer of "Liquid Crystal" sandwiched between two transparent electrode plates(called cells, with a typical monitor being composed of 1280x1024 of these cells), and a back-light(this can be either a fluorescent or LED light source) where this back-light is mearly a source of 'white light'. when a voltage is put between the two electrode of the "cell" the liquid crystals molecules will change posistion and thus change the wavelength of the light passing through it from the backlight and thus creating a certain color to the viewer. by varing this voltage the color can be changed. however the liquid crystal molecules dont hold their posistion for very long, hence the voltage on the electrodes must be continuously switched on and off at a certain frequency to maintain that color, ie the cell must be constantly polarized. now using some control circuitry and thousands of these cells one can create a LCD monitor as we have today.

LED DISPLAYS
LED(light emitting diode) displays are different from LCD displays in a few ways. These differences are:
1. LED displays do not need a backlight.
2. LED displays do not need their cells to be constantly polarized.
3. LED displays have a faster response time as the time it takes to create a color pixel on a LCD is longer than that of a LED.
4. LED displays use LEDs to create a picture where as a LCD uses lots of "liquid crystal cells" to create a picture.
The operation and control of a LED monitor is very similar to that of a LCD. except that a LED monitor needs no backlight as a source of light as LEDs create there own light. also where as LCD monitors only need one cell to create one pixel of one color, a LED monitor needs 3 LED's in one cell to create one pixel of one color, this because is LEDs by nature can only create one color. so in a LED monitors cell you will have a one LED that creates Blue light, another that creates Red light and another that create Green light, a thus allowing this cell to create any color. (im sure everyone knows hows a LED works so i wont explain that). and hence using thousands of these cells ie: 1280x1024 you can create a LED monitor.

And there you have it... the differences between the two types of LCD and LED displays technologies. by reading this one can see that differences in complexity and operation of the two. NOW YOU KNOW HOW IT WORKS 

posted on February 20th, 2010, 9:38 am

Thanks you, about time people knew the difference 

It's obvious there must be difference, why would you pay different amounts for something that does the same job after all 

posted on February 20th, 2010, 3:38 pm

Aye, glad that you posted this, as I was getting a bit ticked off (in the background)

posted on February 20th, 2010, 3:46 pm

There was recently a off topic debate in the "ideas and requests" section of the forum which was started by borg101 on LCD and LED displays. now from that i can see that many ppl dont know the technological design differences between LCD and LED displays, so i thought that i myself being a Electrical Engineer shall set the record straight.

LCD DISPLAYS
A LCD(liquid crystal display) display works by having a layer of "Liquid Crystal" sandwiched between two transparent electrode plates(called cells, with a typical monitor being composed of 1280x1024 of these cells), and a back-light(this can be either a fluorescent or LED light source) where this back-light is mearly a source of 'white light'. when a voltage is put between the two electrode of the "cell" the liquid crystals molecules will change posistion and thus change the wavelength of the light passing through it from the backlight and thus creating a certain color to the viewer. by varing this voltage the color can be changed. however the liquid crystal molecules dont hold their posistion for very long, hence the voltage on the electrodes must be continuously switched on and off at a certain frequency to maintain that color, ie the cell must be constantly polarized. now using some control circuitry and thousands of these cells one can create a LCD monitor as we have today.

LED DISPLAYS
LED(light emitting diode) displays are different from LCD displays in a few ways. These differences are:
1. LED displays do not need a backlight.
2. LED displays do not need their cells to be constantly polarized.
3. LED displays have a faster response time as the time it takes to create a color pixel on a LCD is longer than that of a LED.
4. LED displays use LEDs to create a picture where as a LCD uses lots of "liquid crystal cells" to create a picture.
The operation and control of a LED monitor is very similar to that of a LCD. except that a LED monitor needs no backlight as a source of light as LEDs create there own light. also where as LCD monitors only need one cell to create one pixel of one color, a LED monitor needs 3 LED's in one cell to create one pixel of one color, this because is LEDs by nature can only create one color. so in a LED monitors cell you will have a one LED that creates Blue light, another that creates Red light and another that create Green light, a thus allowing this cell to create any color. (im sure everyone knows hows a LED works so i wont explain that). and hence using thousands of these cells ie: 1280x1024 you can create a LED monitor.

And there you have it... the differences between the two types of LCD and LED displays technologies. by reading this one can see that differences in complexity and operation of the two. NOW YOU KNOW HOW IT WORKS 

Hmm

The problem is not the undestanding. It's the incorrect product desciption.
What you can buy as an LED Display ( Sony Bravia LED for exmample) is a LCD with LED Blacklight.

Don't know if there is a real LED Display on the Market.

posted on February 20th, 2010, 3:52 pm

Sony makes a true LED display its made from OLED as is like $10,000 well i guess that was about a year ago now so someone else make have made one for cheaper by now.

[UnknownSaiyan]

posted on February 20th, 2010, 4:46 pm

Last edited by UnknownSaiyan on February 20th, 2010, 5:23 pm, edited 1 time in total.

My brother was talking about what is sold, and I hope your getting ready to read a very long post about that, because i'm sure he will be working on one as soon as he sees this thread. 

Edit: spelling

posted on February 20th, 2010, 4:56 pm

Oh my gosh... *facepalm*

This is the last Post I will ever place on this thread


you will regret this dethincarn

posted on February 24th, 2010, 3:56 pm

Actually deathincarn was dead on the money.  And the only true LED television on the market at this point is Sony's XEL1.  An 11" screen with an onscreen (what you can see on the screen at any given time.) of 1 million to 1.  It is technically an OLED (Organic light emitting diode).  OLED's have the potential power to have much more color, contrast, use much less power, smaller (and even flexible).  The XEL1 runs about 2,300 bucks.  Rumormills around Sony Electronics is that there possibly could be a larger version (possibly 40") this year.  Its only rumors at this point, but if it does come out....it will be pricey!!  

Good post though deathincarn! 

posted on February 24th, 2010, 3:57 pm

Aye, glad that you posted this, as I was getting a bit ticked off (in the background)

I hope not at me Dom!!

posted on February 24th, 2010, 6:53 pm

I wonder if there is still any good on keeping a CRT. I heard that they don't get images burned into the screen as easily as LCD. Would LED screens have this problem? If not then maybe I can replace my CRT TV screen with a LED TV.

posted on February 24th, 2010, 7:01 pm

@ 1337 Gamer:

i think that ONLY CRTs actually have the issue of pictures being burned onto the screen when displayed for too long.. but i could be wrong here

posted on February 24th, 2010, 7:06 pm

i think that ONLY CRTs actually have the issue of pictures being burned onto the screen when displayed for too long.. but i could be wrong here

if my mind serves me right, plasma screens can also "burn in" pictures
but to gamer, a rt if heavier, and bigger as a lcd screen. the only pros they have are the pretty small price right now and that they can have more pixel/cm²  than flatscreens ( my old CRT had 17" and a resolution of 1600x1200; didnt see an afforable flatscreen reaching that mark)

posted on February 24th, 2010, 7:07 pm

Unless you want an 11" tv you won't find an LED television.  OLEDs don't have problems with burn-ins....though even in todays LCD and plasmas you are very very very very very unlikely to get one.  Even image retention is virtually gone....though in plasmas you have to run a program for your tv for about 2 weeks to help make it "IR proof."

There are some people who want to see companies make CRT HDTVs....but that won't happen.  LCD's are 85% lighter, use less power, cheaper to make higher resolutions, etc, etc.  CRT's have the best motion refresh and resolution (image quality changes in televisions when movement occurs/increases), plasmas are 2nd, and LCD's are next.  Though most all motion problems have been corrected in LCD's w/ 240JHz tvs.  OLEDs obviously beat them all but are so new/pricey I don't include them.

Now is the time to buy consumer electronics though.  End of the fiscal year-ish is usually the best time because new products are being unveiled.  Feb-April stuff will be really cheap.....anything after April, you'll have a hard time finding stock of most of your bigger electronics because companies usually have sold the majority of their inventory by then.

posted on February 24th, 2010, 7:09 pm

I wonder if there is still any good on keeping a CRT. I heard that they don't get images burned into the screen as easily as LCD. Would LED screens have this problem? If not then maybe I can replace my CRT TV screen with a LED TV.

CRT's were susceptible to burn-ins but not image retention....though most confuse the two.