PenTile matrix family
PenTile matrix family refers to a family of patented subpixel matrix schemes used in electronic device displays. PenTile is a trademark of Samsung.
These subpixel layouts are specifically designed to operate with a proprietary set of subpixel rendering algorithms embedded in the display driver, allowing plug and play compatibility with conventional RGB Stripe panels.
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[edit] History
"PenTile Matrix" (a neologism from penta-, meaning "five" and tile) describes the geometric layout of the prototypical subpixel arrangement developed in the early 1990s.[1] The layout consists of a quincunx comprising two red subpixels, two green subpixels, and one central blue subpixel in each unit cell. It was inspired by biomimicry of the human retina which has nearly equal numbers of L and M type cone cells, but significantly fewer S cones. As the S cones are primarily responsible for perceiving blue colors, which do not appreciably affect the perception of luminance, reducing the number of blue subpixels with respect to the red and green subpixels in a display does not reduce the image quality.[2] This layout is specifically designed to work with and be dependent upon subpixel rendering that uses only one and a quarter subpixel per pixel, on average, to render an image. That is, that any given input pixel is mapped to either a red centered logical pixel, or a green centered logical pixel.
PenTile was invented by Candice H. Brown Elliott. The technology was licensed by the company Clairvoyante from 2000 until 2008, during which time several prototype PenTile displays were developed by a number of Asian LCD manufacturers. In March 2008, Samsung Electronics acquired Clairvoyante’s PenTile IP assets. Samsung then funded a new company, Nouvoyance, Inc. to continue development of the PenTile technology.[3]
[edit] PenTile RGBW
PenTile RGBW technology adds a white subpixel to the traditional red, blue, and green subpixels in a color display allowing a brighter display using less power.[4]
The PenTile RGBW layout uses each red, green, blue and white subpixel to present high-resolution luminance information to the human eyes' red-sensing and green-sensing cone cells, while using the combined effect of all the color subpixels to present lower-resolution chroma (color) information to all three cone cell types. Combined, this optimizes the match of display technology to the biological mechanisms of human vision.[5] The layout uses one third fewer subpixels for the same resolution as the RGB Stripe (RGB-RGB) layout, in spite of having four color primaries instead of the conventional three, using subpixel rendering combined with metamer rendering. Metamer rendering optimizes the energy distribution between the white subpixel and the combined red, green, and blue subpixels: W <> RGB, to improve image sharpness.
The display driver chip has an RGB to RGBW color vector space converter and gamut mapping algorithm, followed by metamer and subpixel rendering algorithms. In order to maintain saturated color quality, to avoid simultaneous contrast error between saturated colors and peak white brightness, while simultaneously reducing backlight power requirements, the display backlight brightness is under control of the PenTile driver engine.[6] When the image is mostly desaturated colors, those near white or grey, the backlight brightness is significantly reduced, often to less than 50% peak, while the Liquid Crystal Display levels are increased to compensate. When the image has very bright saturated colors, the backlight brightness is maintained at higher levels. Since most natural images and black on white text have few simultaneously bright and saturated colors, the average power of the PenTile RGBW panel is 50% less than a conventional RGB LCD. Since the LCD backlight is the major power using component on many portable devices such as cell phones and personal media players, products that use the PenTile RGBW panel have longer battery life. The PenTile RGBW also has an optional high brightness mode that doubles the brightness of the desaturated color image areas, such as black&white text, for improved outdoor view-ability.
The Motorola es400 and Motorola Atrix 4G[7] cell phones use PenTile RGBW LCD displays.[8]
[edit] PenTile RGBG
PenTile RGBG layout uses green pixels interleaved with alternating red and blue pixels. The human eye is most sensitive to green, especially for high resolution luminance information. Thus the RG-BG scheme creates a color display with one third fewer subpixels than a traditional RGB-RGB scheme but with the same measured luminance display resolution.[9][10] This is similar to the Bayer filter commonly used in digital cameras.
The Google/HTC Nexus One Android phone uses an AMOLED display by Samsung that uses PenTile RGBG technology as does the Samsung S8000 (although this is stated via numerous sources and can be verified with a magnifier, no information directly from Samsung states this) .[11] The Samsung i9000 Galaxy S and Samsung Wave S8500 series phones use a Super AMOLED PenTile RGBG panel. The Samsung NX10 camera also uses the PenTile AMOLED display for the rear screen.[12] The newly released Galaxy Nexus phone also carries a PenTile RGBG Super Amoled 720p HD display.[13] Dell Venue Pro Windows Phone 7 phone has a 800x480 PenTile RGBG AMOLED display too, but testing on stipple images shows no visible color fringing like on Nexus One[citation needed].
[edit] Controversy
An early controversy regarding the definition or measurement of resolution of color subpixelated flat panel displays in general, and for subpixel rendered displays in particular, led many people to question the resolution claims of PenTile display products.[14] One school holds that resolution is defined by the number of red, green, and blue subpixels, in groups of three, in an array in each axis.[citation needed] The other school holds that resolution is found by counting the number of line pairs, black & white (or bright and dark) lines and spaces that may be simultaneously rendered on the screen, in each axis.[10]
The origin of the controversy surrounding measuring resolution lies in the fact that for RGB stripe color subpixelated displays, both definitions give the same measurement.[10]
However, not all color displays have well defined RGB triplets (e.g. color Cathode Ray Tube). The display industry standard method of measuring and defining resolution in color displays, as originated by the Video Electronics Standards Association (VESA) currently maintained by the International Committee for Display Metrology of the Society for Information Display, is to measure the contrast of line pairs, requiring a minimum of 50% Michelson Contrast for displays intended for rendering text.[15]
The developers of PenTile displays use this VESA criterion for contrast of line pairs to calculate the resolutions claimed.[16] However, for the same resolution and size the PenTile screen can appear grainy, pixelated, speckled, with blurred text on some saturated colors and backgrounds when compared to RGB stripe color.[17] This effect is understood to be caused by the restriction of the number of subpixels that may participate in the image reconstruction when the color is fully saturated. In the RGBW case, this is caused as the W subpixel will not be available in order to maintain the saturated color. In the RGBG case, this will occur when the color is saturated red, as the fully populated (one green per pixel) will not be available. For all other cases, text and especially full color images are fully reconstructed.
[edit] See also
[edit] References
- ^ Tim Oren. "Pentile Matrix: 50% Flat Panel Power Saving Now, More to Come". http://due-diligence.typepad.com/blog/2007/06/pentile_matrix_.html. Retrieved 2011-08-02.
- ^ [1] Brown Elliott, C.H., "Reducing Pixel Count without Reducing Image Quality", Information Display Magazine, December, 1999
- ^ Nouvoyance. "Press Release: Samsung Electronics Acquires Clairvoyante’s IP Assets". http://www.nouvoyance.com/news-031908.html. Retrieved 2010-08-19.
- ^ Nouvoyance. "PenTile RGBW Technology, What does it do?". http://www.nouvoyance.com/technology-what.html. Retrieved 2010-03-03.
- ^ Nouvoyance. "PenTile RGBW Technology". http://www.nouvoyance.com/technology.html. Retrieved 2010-03-03.
- ^ Brown Elliott, Candice, Chapter 12, "Image Reconstruction on Color Subpixelated Displays", Mobile Displays: Technology and Applications, Wiley, 2008, ISBN 978-0-470-72374-6
- ^ Insight Media. "Display Daily - The World's Most Significant New Smart Phone". http://displaydaily.com/2011/01/13/the-worlds-most-significant-new-smart-phone/. Retrieved 2011-01-21.
- ^ Motorola. "Motorola es400 Specifications". http://www.motorola.com/web/Business/microsites/US-EN/ES400/index.html. Retrieved 2010-08-24.
- ^ Samsung Mobile Display. "Visual(=Pentile) Technology". http://www.samsungsmd.com/eng/text/AMOLED/ET-1-1-2.jsp. Retrieved 2010-03-03.
- ^ a b c "Measuring Display Resolution with Contrast Modulation Methodology". Nouvoyance. http://www.nouvoyance.com/files/pdf/CV%20Application%20Note%20Measuring%20Display%20Resolution%20RGB%20L6%2012-17-07.pdf. Retrieved August 20, 2010.
- ^ iFixit. "Nexus One Teardown". http://www.ifixit.com/Teardown/Nexus-One-Teardown/1654/2. Retrieved 2010-03-03.
- ^ Samsung. "NX10 Specifications". http://www.samsungimaging.com/learn/digital-camera-camcorder/productDetailView.do?forward=specifications&prdCtgSeq=205&langPrdSeq=6033. Retrieved 2010-08-24.
- ^ http://www.anandtech.com/show/5000/galaxy-nexus-pentile-discussion-confirmed
- ^ DisplayBlog. "Nexus One "Resolution" Debate Continues". http://www.displayblog.com/2010/04/01/nexus-one-resolution-debate-continues/. Retrieved 2011-07-06.
- ^ Society for Information Display. "International Committee for Display Metrology". http://icdm-sid.org/. Retrieved 2011-07-06.
- ^ Nouvoyance. "PenTile Technology Whitepapers". http://www.nouvoyance.com/downloads.html. Retrieved 2011-07-06.
- ^ Tested Blog. "How PenTile Displays Are Brighter But Not Always Better". http://www.tested.com/news/pentile-vs-real-stripe-amoled-displays-whats-different/1868/. Retrieved 2011-07-27.
