Apple intensifies research into quantum dot-enhanced displays

Posted:
in General Discussion edited February 2014
A trio of patent applications published by the U.S. Patent and Trademark Office on Thursday reveal Apple is conducting in-depth research into quantum dot-enhanced electronic device displays.

Quantum Dot
The iPad on top uses Quantum Dot Enhancement Film from Nanosys.


Taken together, Apple's three patent filings describe an advanced system in which quantum dots are disposed across a device display to offer richer colors, better off-axis viewing and overall better performance when compared to a conventional LCD screen.

Apple was first discovered to be working on quantum dot-enhanced displays when the USPTO published a patent application in December, which outlined the use of a dichroic filter to more accurately control luminance.

Thursday's documents are titled "MEMS shutter control for a display utilizing quantum dots," "Light mixture for a display using quantum dots" and "Backlight dimming control for a display utilizing quantum dots." Each invention details a piece of a larger mechanism that may one day be implemented in products like the iPhone or iPad as a way to enhance color accuracy without greatly impacting cost.

MEMS
Source: USPTO


Perhaps the most interesting of the three is Apple's microelectromechanical systems (MEMS) shutter control patent. LCD displays are typically constructed with a backlight layer that sends light through a liquid crystal layer, which is responsible for controlling brightness at individual pixels to produce an image.

The backlight is usually composed of LEDs coated with a phosphor to give off a white light that subsequently moves through the liquid crystal layer to produce color. Color gamut refers to the subset of colors the display is able to create and is a function of the spectral width of produced red, green and blue light.

MEMS


As noted in the patent, one way to enhance color gamut is to replace the LED phosphor with quantum dots, or nanocrystals made from a semiconductor material that exhibits special quantum mechanical characteristics. QDs emit light isotropically during excitation from absorbed energy like light.

Especially advantageous to display makers are QDs' light-emitting properties, which are defined by size and shape. This means the dots can be manufactured to emit very narrow spectrums of light that in turn produce wide color gamuts.

Apple points out, however, that fabricating a backlight structure with integrated QDs would add unwanted complexity to the system considering the dots' light-emitting properties. At the same time, integrating them within the liquid crystal layer is also problematic. Liquid crystal mechanisms require light to be polarized in order to control color and brightness, and QDs emit un-polarized light.

To successfully position the QDs outside of the backlight structure, Apple proposes the complete replacement of the liquid crystal layer with a MEMS shutter control layer. By performing the swap, the display is able to maintain accurate color provided by QDs while at the same time keeping the backlight architecture largely untouched.

MEMS
Illustration of MEMS shutter.


In one embodiment, the MEMS mechanism is composed of a conductive line, or trace, attached to a shutter. An energy source operably connected to a display controller can provide current to the conductive line, which causes it to become attracted to a static line located in such a way that the optical shutter is pulled closed.

The stackup is composed of a backlight, glass panel, MEMS shutter, QD layer and cover glass. Light moves from the backlight through the MEMS shutter and into the QD layer, which in turn emits a specific light in the spectrum. Emitted light can be mixed to reproduce a large color gamut and fine tuned to display images.

Moving to the "Light mixture" document, Apple provides a completely different application of QDs that implements the sheet within a backlight stackup. As mentioned in the above filing, such integration causes issues stemming from the isotropic properties of the QDs and a backlight's emitted light. Problems include non-uniform brightness, color mixing and inaccurate color representation.

Mix


In this model, a liquid crystal layer is disposed over a backlight stackup. The backlight may be direct or edge-type, but instead of being coated with a phosphor layer tuned to output white light, a QD sheet is used. For example, a blue LED -- used for its naturally narrow spectrum -- or UV light can excite QDs, which emit pure color light to the liquid crystal layer.

Problems occur when a QD sheet is too close or too far from a light source, however. The dots may move from excessive heat or the light mix may be poor due to refraction and uneven intensity. To overcome these issues, the patent goes into great detail regarding the use of prisms, diffusers and light guides. With the right combination, a backlight sub-stack may be produced that is not only more accurate, but thinner than existing modules.

Mix


Finally, Apple's "Backlight dimming" invention takes the previous QD-enhanced backlight system and fine tunes it to correct for LED color shift.

In practice, the QD backlight may have dots arranged in RGB groups so that the light, when mixed, produces a white output. Other embodiments call for a blue LED and groups of red and green QDs. In this example, the blue light mixes with emitted red and green light from the QDs to produce white light.

Backlight


As with common LCD panels, the backlight's brightness may be altered through a reduction in supplied current to affect output intensity. However, in a QD backlight stackup such a change would cause a shift in wavelength of light emitted by the blue LED.

By tuning pulse width modulation, the luminance value of light output by the LED can be controlled to within certain parameters, thus minimizing wavelength shift. For example, luminance can be monitored for a set threshold value. If that threshold is breached, a display controller can adapt the duty cycle and drive current to maintain luminance, but keep wavelength shift to a minimum.

At this point it is unknown if Apple will use its QD tech in near-future product applications, though the tech is already being used in other devices like televisions.

Apple's MEMS shutter control and light mixture patent applications credit Shawn R. Gettemy, Jean-Pierre S. Guillou and David A. Doyle as its inventors. The backlight dimming control patent credits Chenhua You and Jean-Jacques P. Drolet as its inventors, while all three applications were filed on Oct. 31, 2012.
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Comments

  • Reply 1 of 39
    cnocbuicnocbui Posts: 3,613member
    Mechanical moving parts in a display?

    No thanks.
  • Reply 2 of 39
    DLP works well, you know ..
  • Reply 3 of 39
    Quote:

    Originally Posted by cnocbui View Post



    Mechanical moving parts in a display?



    No thanks.

     

    Quote:

    Originally Posted by Hydrogen View Post



    DLP works well, you know ..

     

    Maybe you both need to read a bit more about quantum mechanics and quantum effects before writing nonsense.

  • Reply 4 of 39
    dugbugdugbug Posts: 283member
    Pwm for brightness control is a useful trick for this but I wonder what frequency they would have to use. Hopefully much higher than we can detect
  • Reply 5 of 39
    nagrommenagromme Posts: 2,834member
    capasicum wrote: »

    Maybe you both need to read a bit more about quantum mechanics and quantum effects before writing nonsense.

    They were both talking about MEMS. See the article above.
  • Reply 6 of 39

    You had me at un-polarized light.

    I find it odd I cannot use an iPhone in landscape mode while wearing polarized glasses.

  • Reply 7 of 39
    I think there is no moving part there, the shutters are form memory alloys that change shape when current is applied.

    So they replace LCD slow, subject to aging and limited lifetime, polarized by fma who are very fast, dont wear and are unpolarized. nothing but benefits if it can be done cheaply enough. As usual in tech, it is probably only a matter of doing it mass production style and Apple volumes are high so no worry.

    They would be also probably be finer than LCD film.

    Only hurdle i see is alignement. The other one of memory alloys, sensibility to magnetic fields, is probably not bad as fields strong enough to do damages would also damage computer or phone.
  • Reply 8 of 39
    imemberimember Posts: 247member

    If Apple uses QLED in their future products that means QLED its better than LCD

  • Reply 9 of 39

    Told you. What’d I say? Been saying it for years. They’re not doing OLED.

  • Reply 10 of 39
    Quote:

    Originally Posted by Tallest Skil View Post

     

    Told you. What’d I say? Been saying it for years. They’re not doing OLED.


    Nice, Why would they use something worse than LCD 

  • Reply 11 of 39
    solipsismxsolipsismx Posts: 19,566member
    But Apple doesn't do any research into display technology?¡

    Told you. What’d I say? Been saying it for years. They’re not doing OLED.

    OLED has many benefits over LCD for something like a watch display. You not only get a true blacks for areas that the display not being used with leads to a more pleasing aesthetic in something that is still used as functional jewelry but you also get power efficiency since that part of the display will not be using power.

    Could this mean having a watch face you can leave on all day because it's just thin lines for a digital display (think Apple's new font change for iOS 7) or thin lines for the hour and minute hands (have to touch it to see the seconds hand)?
  • Reply 12 of 39
    This is real pretty but how about some research into making displays that can be written and drawn on better.
  • Reply 13 of 39
    cnocbuicnocbui Posts: 3,613member
    Quote:
    Originally Posted by iMember View Post

     

    Nice, Why would they use something worse than LCD 




    It's not worse.  Arguably Samsung should have had user adjustable saturation sooner and not gone for a default that was over-saturated, but the tech itself is superb.

  • Reply 14 of 39
    This also sounds like it could produce some eye-popping razor-thin 4K monitors or TVs.
  • Reply 15 of 39
    Quote:

    Originally Posted by SolipsismX View Post



    But Apple doesn't do any research into display technology?¡

    OLED has many benefits over LCD for something like a watch display. You not only get a true blacks for areas that the display not being used with leads to a more pleasing aesthetic in something that is still used as functional jewelry but you also get power efficiency since that part of the display will not be using power.



    Could this mean having a watch face you can leave on all day because it's just thin lines for a digital display (think Apple's new font change for iOS 7) or thin lines for the hour and minute hands (have to touch it to see the seconds hand)?

    Not so many than the LCD has over OLED, i dont see a bright future for a flexible display for example how about "sorry i can my post my idea cuz i'm afraid Samsung will read it and steal it" that could only mean bye bye OLED

  • Reply 16 of 39
    cnocbuicnocbui Posts: 3,613member

    Since Samsung demonstrated the world's first full colour QD display, I think they aren't too worried about OLED being surpassed as they will likely be the ones doing it.

  • Reply 17 of 39
    Quote:
    Originally Posted by cnocbui View Post

     



    It's not worse.  Arguably Samsung should have had user adjustable saturation sooner and not gone for a default that was over-saturated, but the tech itself is superb.


    Yes i heard OLED was improved inclunding brightness now LCD and OLED are pretty much equal.

    Test info:

                       OLED                                                             LCD                                                                            

                       True Black   Good                                           True Black   Medium                             

                        Outdoor Visibility   Medium                              Outdoor Visibility   Good

                         Viewing Angle      Medium                                Viewing Angle      Good

                         Viewing Angle Brightness    Medium                  Viewing Angle Brightness   Good

     

    not sure about OLED having accurate colors but if u say that was improved ok then

  • Reply 18 of 39
    Originally Posted by iMember View Post

    OLED                                                             LCD                                                               

    True Black   Good                                           True Black   Medium                             

    Outdoor Visibility   Medium                              Outdoor Visibility   Good

    Viewing Angle      Medium                                Viewing Angle      Good

    Viewing Angle Brightness    Medium                  Viewing Angle Brightness   Good


     

    Because the entire Internet hates the tab key, table version!

     





























      LCD OLED
    True Black Fair Good
    Outdoor Visibility Good

    Fair

    Viewing Angle Good

    Fair

    Brightness Good Fair

     

    Thanks, table, for making yourself too wide for no reason.

  • Reply 19 of 39
    Quote:
    Originally Posted by Tallest Skil View Post

     

     

    Because the entire Internet hates the tab key, table version!

     





























      LCD OLED
    True Black Fair Good
    Outdoor Visibility Good

    Fair

    Viewing Angle Good

    Fair

    Brightness Good Fair

     

    Thanks, table, for making yourself too wide for no reason.


    Lol, it looks better Thanks!

  • Reply 20 of 39
    Quote:
    Originally Posted by Tallest Skil View Post

     

    Told you. What’d I say? Been saying it for years. They’re not doing OLED.


    I don't think the problems with OLED are insurmountable, but given the solutions afforded by QD technology (integrated with LCD and/or MEMS), there is certainly less need to solve OLED's problems (like scaling up to larger sizes at a reasonable cost and achieving a reasonably long lifetime).

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