With the introduction of the Galaxy S4 and its 440 PPI PenTile OLED display, a new bar has been set for high resolution OLED displays and for high performance smartphones.
Friends and colleagues have heard me repeat an old expression, “ There is no such thing as being too thin or too rich.” When it comes to displays it seems that there is a similar thing that can be said that a display cannot be too thin or too high in resolution. In point of fact there are people who are too thin and there are limits to how much resolution can be seen. But, we are not at that top end resolution yet. My prediction is that the march toward increasingly higher resolution will end only when we get to 600 PPI. The reason for this is that there are people who can focus (accommodate) a display at very close distances and can also resolve 50 cycles/degree. Consequently, there will be some people who can still perceive pattern visibility. At 440 PPI the PenTile OLED in the Galaxy S4 has exceeded the ability to see pattern visibility for all but those very few people with better than average accommodation and visual acuity.
At 440PPI the only way to retain the brightness and lifetime of an OLED display is with PenTile technology. Don’t get me wrong, Samsung has made great strides in pushing their resolution capability to higher levels for both RGB stripe OLED as well as for PenTile OLED. There have been reports that this is a result of combining PHOLED for improved red and green efficiency and OLED technology for blue (bit.ly/X51DsE). Such a technique would allow for red and green subpixels to occupy still smaller percentages of the display real estate. If a 440 PPI PenTile OLED is possible, then, by definition, an RGB stripe at 293 PPI is also possible. That said, even for a 293 PPI display if one uses PenTile technology one can push up the brightness to improve outdoor viewability—a better choice for most users.
One blog today (http://bit.ly/15cQhWP ) quoted me as saying that there is no technical solution for replacing PenTile in OLED smartphone displays on the horizon. This is due to the inherent weakness in blue OLED materials, as confirmed to me by Professor Ching Tang, the inventor of OLED technology. He said that the energetics involved in blue quantum excitation was at just at the right level to break the bonds in the OLED materials which means that there’s no solution in the forseeable future for improved blue OLED efficiency.
Can OLED displays extend beyond 440 PPI? Only time will tell.
Galaxy S3 beats iPhone5 for best device of 2012 according to Lindsey Turrentine of CNET.
After reviewing the 10 best and most influential tech products of the year CNET found the Galaxy S3 as the leader and “worldwide hero”. She specifically cited the large, vibrant HD display as a key attribute. This phone uses a 300PPI HD PenTile RGBG OLED display.
It seems that all that I am able to blog about this week are industry pioneers who have passed away. Perhaps this has more to say about the maturity of our industry then about the health of our contributors. There was a nice writeup in Forbes http://onforb.es/TxgI34
Hill started out as a newspaper writer for 20 years in Scotland. In 1986 he joined Aldus to work on the development of their PageMaker layout program. He moved on to work at Microsoft in 1994 to run its typography group and left Microsoft in 2009 to work on screen-reading projects. He died last Wednesday of a sudden heart attack. He will be most remembered for his contributions in the development of ClearType, the application of subpixel rendering to the display of fonts. It is difficult to imagine anyone who has not had the use of ClearType in today’s world.
Without question Bill Hill will be one of those people who so many will miss.
On November 13th the digital imaging industry lost one of the key pioneers, Bryce Bayer, who died in Bath, Maine at the age of 83. http://bit.ly/Tq3jOT While working at Kodak he understood the key issues associated with digital cameras even before there were any digital cameras. He used his knowledge of human vision to design a color filter layout for imaging sensors that more closely mimicked how the human vision system perceived images to more efficiently capture higher resolution images. Our eyes primarily see luminance in green and resolve primarily through the modulation of luminance, rather than chrominance. By developing a layout of filters that populated colors in ration of 25% red, 50% green, and 25% blue it was possible to emulate the manner in which the human vision system primarily uses luminance to resolve details. The layout he used is shown below:
Bayer color filter pattern
Today this layout is universally used in all digital still cameras and smartphone cameras to enable ultra-compact cameras to capture images that are far better than would have otherwise been possible. We owe Bryce Bayer an enormous debt of gratitude for his fundamental inventions in digital imaging and digital photography. No doubt he will be missed by many.
There is one organization that is more focused than any other on displays—the Society for Information Displays, now celebrating its 50 year anniversary. Display Week is held each year as a gathering of the world’s display experts. After evaluating every new display component that has been introduced into products this past year SID selected the display in the Samsung Galaxy Note for the gold award winner. You might recall that the display in the Samsung Galaxy S won this award last year. So, for two years in a row a PenTile OLED panel has been awarded this coveted honor.
Shown below is T K Lee of Samsung SMD accepting the award at SID’s awards luncheon event.
Here is a photo of the Galaxy Note Gold Award winner exhibit in the Samsung booth.
So if the world’s experts in displays, who also generated he first comprehensive standard for display metrology published May 31, 2012 have judged this PenTile display as the best how can it be that so many bloggers persist in finding fault with PenTile displays? It is time to recognize the impact that PenTile has had on the display industry and the quality that it offers.
Shown below is the Samsung SID booth.
Amongst the roughly 30+ displays that were shown this about one half of these were PenTile displays, including the PenTile Super AMOLED displays used in the Galaxy Note, the Galaxy Nexus, the Galaxy Prime, the Galaxy Nexus and the newly announced Galaxy SIII smartphones. Samsung also exhibited their line of mirrorless digital SLR cameras, each of which uses a 3-inch VGA PenTile OLED display.
It is all too easy to forget where good ideas come from. I wanted to pass along a link to an article in the Rochester Democrat and Chronicle talking about Professor Ching Tang the inventor of OLED technology, who in the 1980s was at Kodak, but is today a professor at the University of Rochester. http://on.rocne.ws/JTBLfT
Last year he was awarded the coveted Wolf Prize in chemistry. I have to wonder if he ever imagined the impact his idea would have 30 years later. Together with his colleague, Steven Van Slyke, many patents were awarded for this technology.
Professor Ching Tang from Democrat and Chronicle
Many bloggers have picked up on comments that Philip Berne of Samsung made at a recent press event. He explained that the reason that Samsung chose PenTile Super AMOLED over RGB stripe AMOLED was that of lifetime, specifically that of blue subpixels. He is exactly right, but let me explain this a little more.
AMOLEDs have lifetime that is related to the current density used to drive the OLED material. This is especially true for blue since blue has the lowest brightness for a given amount of current. The other way to say this is that blue OLED material has lower luminous efficiency. To maintain the same brightness with blue, OLED display designers have to drive it with more current per unit area.
So how does PenTile technology help Samsung to extend lifetime for high resolution panels?
This comes from the ability to use 2/3s the number of subpixels in PenTile OLED (Super AMOLED) relative to RGB stripe OLED (Super AMOLED Plus). Thanks to PenTile technology’s use of subpixels rendering it is possible to have the same number of pixels as the equivalent RGB stripe. With only 2/3s the subpixels, one can make the ratio of driven subpixel area larger with a smaller overall percentage of space in between subpixels (better fill factor), as compared to RGB stripe – which is what gives rise to the improvement in current density for a given brightness, which in turn leads to better lifetime.
For lower pixel pitch, such as was used in the Galaxy S Plus, the current density was relatively low due to the coarser pixel pitch so the lifetime was fine. But, at the pixel density of the Galaxy Nexus or the Galaxy S III, PenTile is the way to go, at least until sometime in the future when significant strides are made in blue OLED material luminous efficiency. As I have said before, PenTile is an enabler that make high resolution OLED practical for the product brightness and lifetimes specs that we all have come to demand. This is why you have never seen any production OLED of greater than 250 dpi without a PenTile configuration. If the demand for ever increasing pixel pitch continues, PenTile will still be key even if blue luminous efficiency sees some level of enhancement.
Samsung Galaxy Note Superbowl Ad
With all of the focus on the Superbowl and the Superbowl ads it was gratifying to see two ads for PenTile equipped products in a single Superbowl. One was for the Galaxy Note with a 5.3-inch diagonal 800 x 1280 format PenTile OLED display http://bit.ly/yW5brS The other ad was for the Motorola RAZR with a 4.3-inch qHD format PenTile OLED display. http://huff.to/wqqHYr
By my count today PenTile has shown up in 118 products to date.
For those who would like more information about PenTile OLED and PenTile RGBW technologies for mobile products, you may wish to attend the up coming talk by Nouvoyance CEO Candice Brown Elliott in Southern California, “AMOLED vs. Hi-Res LCD for Premium Cell Phones”. She will be speaking at the Los Angeles Society for Information Display Chapter’s annual symposium on “Emerging Display Technologies” on February 3rd, 2012. For more information regarding attending the symposium, visit the LA SID Chapter website: http://www.sid.org/ConferencesExhibits/LAChapterEmergingDisplayTechConference.aspx
Ms. Brown Elliott will also be speaking in Northern California, at Stanford University on the 28th of February on the topic of “Reducing Field Sequential Color Break-Up Artifacts using a Hybrid Display with Locally Desaturated Virtual Primaries”. This talk will cover the development of the PenTile Hybrid Multi-Primary Field Sequential Color display that was demonstrated by Samsung in their DisplayWeek 2011 booth last May in Los Angeles. For more information regarding attending the talk, visit the Stanford Center for Image Systems Engineering website: http://scien.stanford.edu/
I have noticed a question reoccurring recently about some larger SVGA phones being announced at CES. It can be said in general that an WVGA format (800 x 480) OLED phone with more than 4.1-inch diagonal will be an RGB stripe display rather than PenTile OLED. Such a large WVGA format, such as that in the newly announced Nokia Lumina 900 (4.3-inch WVGA) would be too coarse of a pixel density to recommend PenTile due to increased pattern visibility. For sizes of 4.1″ or less for WVGA it is necessary to use PenTile to enable the manufacturing of a phone that meets the required specifications for an OLED display in a phone. This says nothing about any given manufacturers preference for RGB stripe over PenTile or PenTile over RGB stripe, but a simple decision based upon the size and resolution of the display.