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Tag: Ulrich T. Barnhoefer

  • Recent patent application shows Apple’s interest in improving brightness controls on OLED screens

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    It’s the patent applications that show where things might be going.

    Per Free Patents Online, Apple has apparently proposed a way of improving brightness control on organic light emitting diode displays.

    One of the key advantages of OLED is that, unlike LCD, it does not employ a backlight to illuminate the screen. While this can lead to superior picture quality and improved battery life, it can also make adjusting the brightness of the screen more difficult, Apple notes in a newly published patent application.

    The filing, entitled “OLED Driving Technique,” explains that traditional LCD brightness is adjusted by simply increasing or decreasing the amount of light emitted by a backlight. But that’s not possible with an OLED display, as each pixel on an OLED screen emits light individually.

    That means device makers must adjust the amount of power supplied to each OLED pixel, making it a far more complex endeavor to adjust brightness than an LCD display with a dedicated backlight.

    “While increasing or decreasing the amount of power may increase or decrease the amount of light emitted by each OLED, the precise amount of light emitted by each OLED may vary according to nonlinear function,” Apple’s filing reads. “As such, many techniques for adjusting the brightness of OLED screens have conventionally involved performing complex calculations on image data to ensure that when a brightness-adjusted image id displayed on the OLED display, each pixel displays a proper color and brightness.”

    In other words, the amount of light output by an individual OLED pixel varies nonlinearly with the amount of power supplied to the OLED pixel. As a result, increasing or decreasing the brightness does not directly correlate to simply increasing or decreasing the power supplied to each pixel.

    Apple goes on to explain that dimming values must be extracted from image data on a system, and that data must then be converted to an analog OLED pixel brightness control signal. This complex method can consume system resources and reduce battery life, and it may also be incompatible with existing LCD brightness control mechanisms, requiring major changes to software that already drives LCD screens.

    Apple’s proposed solutions aim to offer “efficient brightness control” with OLED screens. One described method would take image data and transform it into a “logarithmic domain,” from which a “dimming control value” could be subtracted.

    “This resulting log-encoded dimmed image data may represent a darker version of the originally received image data,” the filing reads. “Thereafter, a pixel of the organic light emitting diode display may be driven based at least in part on the dimmed image data.”

    In Apple’s method, image data could be converted in the data driver of an integrated circuit connected to the OLED screen. This data would be converted from a “framebuffer encoding” gamma-corrected color space to a logarithmic value.

    “From this logarithmic value, a digital dimming control value may be subtracted rather than divided,” the filing states. “This dimmed logarithmic image data may be converted directly to an analog OLED pixel brightness control signal, without first being converted to a linear digital value, via a digital-to-analog converter (DAC) programmed to convert the logarithmic digital image data to the OLED pixel brightness control signal.”

    Apple’s solution would enable simplified dimming of OLED, and would convert the data associated with adjusting brightness from digital to analog. But Apple’s method would do so with fewer bits, and would be less taxing on a mobile device like an iPhone, iPad, or MacBook.

    The illustrations accompanying the application specifically show a MacBook Pro as a potential device that could utilize an OLED screen, although the filing notes that Apple’s method of controlling OLED brightness could be used on any device, from smartphones to television sets.

    Apple has shown continued interest in OLED screens through patent filings, with one proposed invention last year that aimed to improve power efficiency of OLED screens. However, some industry watchers have said that OLED technology, and the production of OLED screens, are not yet mature enough to meet Apple’s standards and requirements.

    The latest OLED filing, published this week by the U.S. Patent and Trademark Office, was originally submitted in October of 2010. It is credited to Ulrich T. Barnhoefer and Lee Yongman.

    Stay tuned for additional details as they become available.

  • Apple patent towards HDTV design with additional backlighting features

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    This could turn into something pretty cool.

    Per Free Patents Online, Apple is looking into building displays with dynamic backlight adaptation for better picture quality, particularly when watching letterboxed widescreen movies on a high-definition screen.

    The concept was revealed this week in a new Apple patent application discovered by AppleInsider. The filing, entitled “Dynamic Backlight Adaptation for Black Bars with Subtitles,” focuses on improving picture quality when watching letterboxed content, like Hollywood movies, on an LCD display.

    The application was filed just months ago, in September of 2011, and comes as rumors of a full-fledged Apple television set continue to build. One report this week claimed that Apple design chief Jonathan Ive has a 50-inch prototype set located in his secure work studio at the company’s corporate headquarters.

    A common problem with LCD displays is the ability to show “true” black colors on the screen. This becomes amplified when black bars are included in a video, such as when watching a letterboxed film. The difficulty of adjusting the backlight properly when the black bars are present can result in poorer quality of the remainder of the video.

    Even though modern television sets are built with widescreen 16-by-9 aspect ratios, Blu-ray and DVD films, as well as those sold on iTunes, often show movies in an even wider format, leaving black bars at the top and bottom. For example, many movies are shot in Panavision’s 2.35:1 ratio.

    “Many video images are encoded with black bars, e.g., non-picture portions of the video images,” the filing reads. “These non-picture portions complicate the analysis of the brightness of the video images, and therefore can create problems when determining the trade-off between the brightness of the video signals and the intensity setting of the light source. Moreover, these non-picture portions can also produce visual artifacts, which can degrade the overall user experience.”

    Further complicating picture quality and brightness is the fact that users can often view subtitles in the black bars located at the top and bottom of a widescreen film. This makes it even more difficult for the system to dynamically adjust and ensure the highest level of quality.

    Apple’s solution is a complex processing system that could “spatially vary visual information” on a display. This would dynamically adjust the backlight source on a screen, like a high-definition television set, in a way that would improve the picture quality.

    The display would have multiple brightness settings for its backlight based on the processing of the image. For example, the “picture portion” of the screen would be illuminated by LED backlighting to an appropriate level, whereas the “non-picture portion,” which would include the black bars, would have a different backlight setting.

    The application describes an “extraction circuit” included in the display, which would calculate a brightness metric associated with the video signal. Then an “analysis circuit” would analyze and identify specific subsets of a video, like black bars that are shown when watching a movie.

    The display would also include an “intensity circuit” that would determine the ideal intensity of the light source that illuminates the LCD display. The system could also employ a mapping function to determine optimum quality by using features like a “distortion metric” to limit image distortion.

    Apple’s system could also process the video signal in advance and synchronize the intensity of the light source based on the image currently being displayed.

    “The system determines the intensity setting of the light source on an image-by-image basis for the sequence of video images, where the intensity of the given video image is based on the brightness setting and/or brightness information contained in the video signals associated with the given image,” the filing reads. “Then, the system synchronizes the intensity of the setting of the light source with the current video image to be displayed.”

    The filing, made public this week by the U.S. Patent and Trademark Office, is credited to inventors Ulrich T. Barnhoefer, Wei H. Yao, Wei Chen, Barry J. Corlett, and Jean-didier Allegrucci.

    Though rumors of a full-fledged Apple television set have persisted for years, they picked up once again late last year, when it was revealed that Apple co-founder Steve Jobs told his biographer that he had “cracked’ the secret to building an integrated, easy-to-use television set.

    “It will have the simplest user interface you could imagine,” Jobs said, prompting speculation that an Apple-branded television would use Siri, Apple’s voice control software featured on the iPhone 4S, as its primary input method.

    Stay tuned for additional details as they become available.