Katie Marsal
A new patent application made public by the U.S. Patent and Trademark Office this week describes potential techniques for arranging LED backlights in new ways, and reducing color shift caused by chromaticity (or color quality) variations with LED lighting. Discovered by AppleInsider, the application first filed in February of 2010 is entitled "Backlight Unit Color Compensation Techniques."
In the application, apple notes that LED lighting has replaced fluorescent lighting (CCFLs) to provide backlights for liquid crystal displays. LED has a number of advantages over CCFLs, including higher light output, improved efficiency, lower power consumption, reduced heat, and longer operational battery life.
But due to the manner in which certain LEDs are fabricated, viewing angles — particularly with phosphor-coated LEDs — can be poor. Variations in chromaticity can negatively affect the color uniformity of the display, resulting in an inaccurate picture.
The application explains that though LED light is white, it can have a bluer tint at relatively short distances. As the light travels further from the phosphor layer, it becomes more yellow.
Apple's solution would address the issues associated with edge-lit backlights for LCD displays by utilizing a "light guide" Coupled with a "light-extracting surface area," it could compensate for color shift issues found with current edge-lit displays, like those found in Apple's MacBook Pro notebooks.
A light guide would be "configured to provide for propogation of light received from a light source from a first lateral edge to a second opposite lateral edge. A portion of the received light is allowed to reach the second lateral edge and is retro-propagated back towards the first lateral edge. Multiple light-extracting elements are provided to extract and mix the propagating and retro-propagating light, such that the light emitted from the light guide exhibits improved color uniformity."
The application makes mention of using the backlighting technique in any of Apple's products with LCD displays, including the iPhone, entire line of MacBook notebooks, or the iMac. The proposed invention is credited to Chenhua You of San Jose, Calif., and Shengmin Wang of Hsinchu City, Taiwan.
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33 Comments
Not going for OLED technology?
With current viewing angles almost at 180 degrees, is there any more room to go, really? Maybe the are thinking of transparent displays, like the Tom Cruise movie Minority Report
Can someone please link to the patent application. With something this complex I'm sure many readers would be interested in more detail than a one sentence description. I Googled around for a few minutes, though, unsuccessfully. Why would the author omit such a crucial piece of information?
Not going for OLED technology?
Given the apparent pricing of the larger displays, it's probably not ready yet. Nothing larger than what you'd find in a phone or camera is remotely affordable.
I forget how spoiled we are with Apple’s displays. Not that they have the only nice displays around, but I was just playing with a RIM PlayBook and Galaxy Tab at Best Buy (home of the no-iPads-in-stock) and... wow. For about the same price as an iPad, those 7” screens are absurdly small (yet thick and bulky and non-pocketable); and their poor viewing angle gave them a metallic shimmer straight out of 2009.
Not going for OLED technology?
Nothing about this says that Apple isn’t also interested in OLED; but AFAIK, OLED’s problems (like color shift over time and usage in sunlight) have not yet been solved at any size, much less at large sizes. LED backlit enhanced IPS seems to be the best display that’s practical now, and that’s what Apple uses. Maybe this patent could improve on that! But Apple patents their inventions whether they’re going to ship them or not. A patent really tells us little about their plans.