Apple LED-backlit Laptops?

Mydel

macrumors 6502a
Original poster
Apr 8, 2006
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Sometimes here mostly there
Look what was posted on engadget...Looks interesting. Would love one of those in MBP

While nobody really knows what Mr. Jobs has planned for next week's Macworld keynote, DigiTimes has a report claiming that LED-backlit laptops are coming down the pike, and if true, will be hitting more than MacBook Pros. According to a rather sure-sounding account, Apple and HP are both aiming to launch lappies in the second quarter of this year with LED-based LCD panels. Purportedly aimed to showcase the sexy interfaces that await us in Windows Vista and OS X 10.5, the screens would be derived from suppliers such as "Nichia or Cree" and tout a "brightness level of over 1,680 nits." Additionally, no model names were handed out as potential candidates for the LED upgrade, but with refreshed laptop models from both firms essentially sure to hit within a matter of months, it wouldn't be too surprising to see such upgrades make the cut. Nevertheless, we've seen our fair share of certainties turn out bogus, so per usual, we'd recommend a healthy dose of table salt with this one as well.

What do you think??

http://www.engadget.com/2007/01/03/apple-and-hp-readying-led-backlit-laptops/

Sorry forgot the link....
 

AoWolf

macrumors 6502a
Nov 17, 2003
956
0
Daytona Beach
That would be cool. LED's have come a long way ( and hopefully have a long way to go!) I wonder how much power that would save.
 

Clive At Five

macrumors 65816
May 26, 2004
1,438
0
St. Paul, MN
...what does an LED display mean? how is it different from the current ones?
Instead of a traditional power-devouring backlight, the laptops would use more energy-conscious LEDs to backlight the displays... possibly something similar to those super-bright white LEDs...

The only thing though... Last I checked, for the most part, LEDs only have two settings: on or off. What about different brightness settings? This would not work with LEDs alone... maybe it would with the help of some sort of aperture... but reducing brightness with such a device would not conserve battery life.

-Clive
 

longofest

Editor emeritus
Jul 10, 2003
2,846
1,394
Falls Church, VA
...what does an LED display mean? how is it different from the current ones?
Many current displays use flourescent backlights (cold cathode fluorescent lamp to be precise). The backlight is the most significant power drain in a LCD display, which is why laptop users who turn down their display brightness tend to get better battery life.

Since LED's traditionally use much less power than other light sources, using it as a backlight would cut the power needed to display images. It's been known that LED backlighting has been an up-and-coming technology, but this is the first time its been attributed to Apple.

That being said, the attribution is being done by Digitimes, so don't get your hopes up.

More info on backlights in LCDs.
 

mainstreetmark

macrumors 68020
May 7, 2003
2,228
293
Saint Augustine, FL
Instead of a traditional power-devouring backlight, the laptops would use more energy-conscious LEDs to backlight the displays... possibly something similar to those super-bright white LEDs...

The only thing though... Last I checked, for the most part, LEDs only have two settings: on or off. What about different brightness settings? This would not work with LEDs alone... maybe it would with the help of some sort of aperture... but reducing brightness with such a device would not conserve battery life.

-Clive
Not entirely true. A brightness setting is simulated in LEDs by chopping the voltage. Rapidly switching from the full 5v to 0v at 60hz can produce half-intensity light, and so on...

I wonder if this will make them daylight readable.
 

Clive At Five

macrumors 65816
May 26, 2004
1,438
0
St. Paul, MN
Not entirely true. A brightness setting is simulated in LEDs by chopping the voltage. Rapidly switching from the full 5v to 0v at 60hz can produce half-intensity light, and so on...

I wonder if this will make them daylight readable.
Yes, I forgot about those!

Oy, though! As long as it doesn't have that pulsating look to it... I know 60Hz is faster than the "frame rate" of the human eye, but something about those pulsating LEDs still grinds my gears.

-Clive
 

jettredmont

macrumors 68030
Jul 25, 2002
2,714
307
Yes, I forgot about those!

Oy, though! As long as it doesn't have that pulsating look to it... I know 60Hz is faster than the "frame rate" of the human eye, but something about those pulsating LEDs still grinds my gears.

-Clive
No, you'd want a "flicker" of more like 120-200MHz, perhaps even more, to avoid eye strain. While the typical eye/cortex can only "process" a visible change 30 times a second, the lower-order reflexes respond significantly faster. Strobing of a large portion of the central visible area (ie, a 17" laptop sitting in your lap) would absolutely kill your eye muscles and likely induce major migranes in those of us prone to such.

Remember back when we used tubes and the refresh rates had to be that high? Yeah, same idea, sort of. The problem there was that a small area of the screen would oscillate between full brightness, fade to near-black, then quickly ramp back up to full brightness in that timeframe, wreaking havoc on the reptile-brain bits behind the eye as they tried to react. This would be significantly worse, in that the ramping times would be near-zero (full on, full off, very little phosphor fade, most likely) and the full area of the screen would be blinking in unison.

Of course, then there are other possibilities such as:

* sufficient light spreading to allow that only a fraction of the lights in the display need to be on at a time to offer even lighting.
* "blinking" of different nearby LEDs at different offsets (ie, preventing the whole screen going black for an instant)
* phosphor fade effects to "even out" the blinking of each individual LED to something more like a constant but dimmer light.
 

NorCalLights

macrumors 6502a
Apr 24, 2006
593
76
Yes, I forgot about those!

Oy, though! As long as it doesn't have that pulsating look to it... I know 60Hz is faster than the "frame rate" of the human eye, but something about those pulsating LEDs still grinds my gears.

-Clive
You won't see a flicker. Even LEDs at low levels flicker less than the fluorescent tubes in your office. LEDs are becoming very common in the entertainment industry these days where they are often used at awards shows and the like. TV cameras are very sensitive to flickering sources, but even they don't have a problem.

The only problem that I see is that LEDs do not output a complete set of light frequencies. Even "white" LEDs are missing more of the spectrum than fluorescent tubes are, which means an LED-illuminated screen will have a difficult time reproducing certain colors. They might be fine for a consumer display, but I suspect they would have some trouble with accurate color reproduction in a pro photography or video application.
 

Rend It

macrumors 6502
Oct 27, 2003
265
5
United States
LED brightness adjustment

FYI, this is how it's done:

http://www.national.com/pf/LM/LM27953.html

It's not 60 Hz, nor hundreds of MHz; it's anywhere between 100 to 1000 Hz. Also, LED brightness is a nonlinear function of the electrical current driving it. So, to some extent, it is possible to control brightness by adjusting forward current. However, since the relationship is not precisely linear, engineers prefer to use PWM near the "grouping current" to achieve a linear relationship between duty cycle and brightness.

rendit
 

shamino

macrumors 68040
Jan 7, 2004
3,400
189
Purcellville, VA
The only thing though... Last I checked, for the most part, LEDs only have two settings: on or off.
Really? Years ago, I used to build little hommeade projects with LEDs (the traditional el-cheapo red, green and amber types.) Reduced voltages definitely made them dimmer. But you are right that there is a minimum voltage, below which it won't light at all.

But perhaps the modern types (like the blue and white ones that are so poopular today) behave differently from the old kind.
A brightness setting is simulated in LEDs by chopping the voltage. Rapidly switching from the full 5v to 0v at 60hz can produce half-intensity light, and so on...
Sort of like how incandescent dimmer switches work.
The only problem that I see is that LEDs do not output a complete set of light frequencies. Even "white" LEDs are missing more of the spectrum than fluorescent tubes are, which means an LED-illuminated screen will have a difficult time reproducing certain colors.
It's my understanding that an actual white LED is impossible. Those sold as white are actually blue LEDs that use a phosphor coating to produce a yellow component. The eye perceives the combined blue and yellow as something close to white. But this is clearly not going to be adequate for some applications. Here's Wikipedia's article on the subject.
 

Aniej

macrumors 68000
Oct 17, 2006
1,743
0
Not entirely true. A brightness setting is simulated in LEDs by chopping the voltage. Rapidly switching from the full 5v to 0v at 60hz can produce half-intensity light, and so on...

I wonder if this will make them daylight readable.
This is a good point. An example of this in everyday life comes from break lights in certain high end cars like range rover, bmw and mercedes benz. Another example comes from the lightbars and undercover lights used by some police agencies. Ironically, the two examples that i gave often tend to be paired together when on the road as well.:D

The only problem that I see is that LEDs do not output a complete set of light frequencies. Even "white" LEDs are missing more of the spectrum than fluorescent tubes are, which means an LED-illuminated screen will have a difficult time reproducing certain colors. They might be fine for a consumer display, but I suspect they would have some trouble with accurate color reproduction in a pro photography or video application.
Wait... am I missing something here? I thought we were discussing the keyboard backlighting as a means of illuminating the keys, not something in relation to the actual screen:confused:

Upon further review, it appears it is the display they are talking about. sorry. But, this does have a silver lining. Perhaps this rumor is really true and there is a basic move towards what I said, backlighting the keyboard with an LED, what is currently used for the keyboard illumination? Please don't tell me its an LED it will cap off my already cr*p of a day.
 

balamw

Moderator
Staff member
Aug 16, 2005
19,366
978
New England
It's my understanding that an actual white LED is impossible.
The other approach that has been used it to combine red, green and blue LEDs, the problem is that the reds age quicker than the other two which leads to a shift in the color temperature over time.

Note that typically only 30% of the blue light created makes it out of the phosphor coating as "white" and the buggers are STILL more efficient than any other light source.

B
 

Butthead

macrumors 6502
Jan 10, 2006
440
19
You won't see a flicker. Even LEDs at low levels flicker less than the fluorescent tubes in your office. LEDs are becoming very common in the entertainment industry these days where they are often used at awards shows and the like. TV cameras are very sensitive to flickering sources, but even they don't have a problem.

The only problem that I see is that LEDs do not output a complete set of light frequencies. Even "white" LEDs are missing more of the spectrum than fluorescent tubes are, which means an LED-illuminated screen will have a difficult time reproducing certain colors. They might be fine for a consumer display, but I suspect they would have some trouble with accurate color reproduction in a pro photography or video application.
Incorrect, there are single color white (which tend to be rather bluish, like that you might see in a flashlight), and other single color LED's on die. And there are RGB primary colors on a single die, LED's that can be very accurate with colors, more so than the CCFL backlights currently in LCD screens.. Go to Cree's, or Nichia's websites and read up on them.

However, I think this story is pure bogus speculation. While it is technologically possible, I'm not aware of pricing that would make this possible currently (I could be wrong about that, perhaps we are now at economy of scale just like with NAND memory starting to replace hard drives in iPods, and in a year or two, laptop drives).

I should point out that according to Sharp, in announcing larger sizes of bigscreen LCD TV's earlier this year (or was it last fall?) latest LCD tech was upping the ante as far a color reproduction, but LED backlighting can surpass accuracy of any other LCD tech. LED backlit LCD's have the widest current color gamut, as well as accuracy (other than old some very high-end CRT's). Tests have shown this to be true (I forget which PC centric site published a review). Do a search on NEC's early LED 21in monitor, and you'll find that review re: color accuracy.

http://club.cdfreaks.com/showthread.php?t=195959

What is interesting is that you can see a visible difference in colors being displayed in the demo picture at the link above, but without being there in person, you wouldn't be able to see that full color gamut via images posted on the internet ;).

Samsung's just announced/released 20in XL20 model, designed for professional uses, is naturally quite expensive at $2k list. But they have also announced (hasn't shipped yet, but is supposed to be available now) a 40in LED backlit LCD TV with estimated $3,000 price tag.

http://ledsmagazine.com/articles/news/3/11/6/1

http://www.macnn.com/articles/06/10/25/samsung.xl20.display/

http://www.samsung.com/PressCenter/PressRelease/PressRelease.asp?seq=20061104_0000298342
"Traditional LCD screens typically cover only 82 percent of the NTSC standard color gamut (CRT covers 76 percent), while the new XL20 utilizes a unique light emitting diode back light unit (LED BLU), increasing the color gamut up to 114 percent of the NTSC color gamut.

The LED BLU increases the ability to create significantly enhanced images producing a more natural range of color, and covering the full Adobe RGB natural color space / gamut."


Being the 1st of it's kind the 20in XL20, if engadget is correct on the spec's is a very disappointing brightness of 250nits. While Cree has newer, 70lm/w and 100lm/w very small size efficient LED's, they are leading edge tech, so even in quantity, I doubt you could get them at a low enough cost to produce a screen with 1,6knits; most dubious figure I see in the Digitimes 'rumor'.

http://www.engadget.com/2006/09/22/samsung-busts-out-the-720td-711nd-and-xl20-lcds-in-japan/

OLED (which does not require backlighting, given that technology) in theory would be capable of being more accurate, but last year's announcement by Samsung of a 40in prototype OLED TV, was producing something on the order of only 80% of the NTSC color gamut, IIRC. LED backlit LCD's in large screen TV's are more accurate.

Less accurate color reproduction, lower cost LED's that might be bright enough, could make it into a laptop screen (or desktop monitor, no reason not to have them there) this year, but probably not until later in the year, when prices come down, technology scales up on the latest gen of LED's to make it so.

Best thing about LED backlighting, besides greater color accuracy, wider color gamut, is evenness of illumination of the entire screen, one of the big flaws of current LCD screens used in laptops.
 

hanschien

macrumors 6502
Oct 2, 2006
337
13
Houston, TX
Remember, all of our newer Macs have a dimming LED (sleep light). Maybe it's just me, but I can see a pulsation effect on the sleep light if I move my eyes side to side really fast.
 
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