All posts in New Technology

Not all RGBW Displays are Created Equal

Perhaps you may have noticed that LG introduced an RGBW OLED TV at CES, using a white OLED process together with traditional RGB+Clear color filters.

The purpose of this was ostensibly to facilitate the manufacturing of a large diagonal OLED, that is traditionally difficult with shadow mask deposition techniques.  My assumption is that they used RGBW to enhance brightness, taking advantage of their white OLED material to attain the longer 30,000 hours or more of  lifetime which is now expected for TVs.  At CES I was told that the layout was a QUAD layout, which uses 4 subpixels per pixel, unlike PenTile that uses, on average, 2 subpixels per pixel achieved through subpixel rendering.

Similarly, we are also seeing additional announcements of products by Sony using their Sony Whitemagic™ technology.

The layout of RGBW for Whitemagic also has used 4 subpixels per pixel unlike PenTile’s 2 subpixels per pixel on average.  While Sony’s stated purpose for Whitemagic has been to enhance power efficiency, a 4 subpixel per pixel layout only take advantage of the improved light throughput of clear subpixels.  It is, no doubt, an improvement to power efficiency, but it forgoes the chance to improve aperture ratio, which a significant part of what is achieved with PenTile technology.  As one moves to increasingly higher resolution formats aperture ratio becomes a major limitation, even for low temperature polysilicon (LTPS) backplanes.  For PenTile, however, the contribution of improved efficiency in our highest resolution designs is equally attributable to improvements in aperture ratio as well as the improved throughput gained from clear color filters.

Competitive RGBW is a step in the right direction, but there is no substitute for genuine PenTile technology.

OneIndia Video Post

There was some terrific video coverage of the new Samsung WQXGA, PenTile RGBW 300 dpi tablet panel that was shown at the recent SID DisplayWeek.

While this video mentions other high resolution tablets, no company, other than Samsung, has publicly demonstrated any 10.1-inch prototypes of more than 150 dpi to date.

This video raises lots of interesting questions about the application of this panel to products, but, as I have already said, Samsung is still in the prototype stage of product development  so you will not see any tablets with PenTile RGBW 300 dpi within this year.

Samsung Experience Media Tour

300 dpi PenTile tablet panel

On June 6-7, Samsung hosted a media event in their amazing facility on the third floor of the Time Warner Bldg at Columbus Circle in NYC.

This gave us a chance to show off our 10.1″ WQXGA to editors and bloggers who didn’t have the chance to see this at SID DisplayWeek in LA. Scott Birnbaum VP of New Business Development for Samsung Electronics presented both PenTile and Transparent Display technology that Samsung is now developing. It is always very useful to collect live feedback on our newest displays.

Joel Pollack demonstrating PenTile RGBW display.

Can PenTile RGBW be used for TV?

You bet!

Samsung SEC has built prototypes of a 32-inch FHD TV using PenTile RGBW with a white LED backlight.  This was demonstrated at the 2010 Flat Panel Display International (FPDI) conference in Makuhari, Japan.  This PenTile RGBW LCD  TV runs at about 55% the power of an equivalent brightness legacy RGB stripe panel showing the full range of multimedia applications.  The PenTile RGBW TV is capable of even higher savings for TV or video alone.

Due to the white subpixels, the white areas and reflections from things like the metal in a chrome bumper have a real zing that is not seen in conventional RGB stripe TVs.

Just like the mobile displays these are built with one-third fewer subpixels, but from only 2 meters away the pixels are seen as 48 cy/deg* of human vision where the pattern is not easily seen by the best of eyes.

* 48 cy/deg means that in one degree of human vision one can see 24 white lines and 24 black lines

PenTile Multiprimary SID Display Week Demo

Samsung and Nouvoyance have teamed their efforts and resources to combine three different display technologies into one technology demonstration. These technologies are:

1. PenTile RGBC (cyan) W(clear) color filter layout used with subpixel rendering.
2. An RGB LED 2D backlight that is capable of controlling both color and luminance over an array of zones.
3. Field sequential color (FSC) addressing at a 180 Hz frame rate to write reddish, greenish and bluish fields in sequence.

These technologies combine to achieve:

1. 25% of the power relative to comparable RGB stripe
2. 130% NTSC color gamut
3. Nearly zero level of color breakup artifact

Many people asked why the panel uses both FSC and color filters. The reason is that with the color filters it is possible to further stabilize this panel against these FSC artifacts.

The demos illustrates a new capability resulting from the generation of new LCD and backlight hardware as well as some rather complex algorithms for stitching together images that concurrently use both static color filters and FSC color.

Gizmodo’s ‘Super Clear Displays of the Future’

“The iPhone 4′s beautiful Retina Display is a little less beautiful today. Why? Because at SID 2011, an exhibition about displays, companies have revealed screens that were transparent, tablets that did glasses-less 3D and screens clearer than Apple’s fabled Retina.

Here are the coolest screens from SID 2011:
Samsung 10.1-inch 300ppi display: A display that’s been heard from before, the Samsung 10.1-inch, 2560×1600 display has a pixel density of 300ppi. Which is killer on such a big screen (iPhone’s Retina Display is 326ppi across 3.5inches). The panel uses PenTile RGBW technology (which didn’t do so hot in the Nexus One) but promises to make colors pop and consume 40 percent less power. In any case, it’s still a freaking 10-inch retina display.”

Absolutely thrilled to be featured on Gizmodo’s roundup of the coolest screens from SID 2011.
Thanks for that!

Day 1: SID recap

Visitors to the PenTile SID demonstrations at SID

Day 1 at SID is behind us and we’re pleased to say we had an incredibly busy day. The Samsung/Nouvoyance demonstrations were mobbed, almost to the point that it was difficult to walk through virtually all day. The demos of the new WQXGA 10.1″ tablet display, as well as those for the multiprimary PenTile displays, performed stunningly.  We were glad to see some tech industry experts, including some folks from Engadget, come through and take a tour of the new tablet display.

But we were also pleased to see that the PenTile multiprimary display demonstration got a bigger crowd throughout the day. We are encouraged that this means good things to come for our entire line of PenTile displays.

Demonstration of PenTile Multiprimary Display

Thanks to all who stopped by yesterday. If you’re in the neighborhood of SID, stop by our booth #707 and see the displays for yourself!

300 dpi is Fine but I Would Rather Have IPS

This is not an “either/ or” condition. This a case of having your cake and eating it too. PenTile RGBW technology is perfectly compatible with all types of wide viewing angle technology such as IPS, multidomain (PVA, MVA, etc). In fact, as a power saver it makes it a bit easier to use a wide viewing angle (WVA) technology with PenTile RGBW since many of these WVA techniques reduce light throughput.

IPS (in plane switching) was the name given to a type of WVA technology many years ago by Hitachi and was licensed to other display makers. Other variants of this methodology are in use by Samsung. Samsung uses a few different types of WVA technologies depending upon the application.

Perhaps there are some who are still asking, “Does a tablet PC that is being used by one person who is looking directly at the display really need WVA technology?”. The answer is a definite yes it does. Even a mobile display is used laying on the desk in front of you or held in your hands. Then consider viewing in both portrait or landscape modes and you realize that WVA capability is a generally a good idea.

So, here is the interesting thing about the new Samsung WQXGA PenTile RGBW prototype panel–it has a very wide viewing angle technology, not so different from IPS. Judge for yourself when you come see this at SID Display Week in LA this week.

RE: Expiance’s post on RGBW, PenTile, Subpixels and Graininess of mobile displays

I wanted to take a moment to respond to Alex Taylor’s blog post on last Friday. For starters, I am very impressed at how much thought and work you put into your post, Alex. Well done!

Still, I feel I need to add some clarification and correction to a couple of things you said in your blog.
Many people like yourself who have, for so long, thought of pixels as having a fixed number of dots, typically three per pixel, so it is not surprising you look at this layout and say there are two per pixel. Certainly, on the average that is true, but it is important to think of pixels in a subpixel rendered display as logical pixels.  This is not unlike it used to be for CRTs. How many subpixels are in a CRT spot? A CRT spot is comprised of a Gaussian distribution of light about a logical pixel center. Such logical pixels can overlap, but when the modulation ratio drops below 50% one loses resolution, per the VESA specification.
PenTile works much the same way.  As many as 10 subpixels can be involved in a given logical pixel, so it is misleading to say one pixel lacks blue and the next lacks red or green. Every pixel is addressed at 8 bits/color and each luminance center is lit by the proper combination of the layout and the algorithms that analyze the image and render the display. It is nothing like compression or zipping.

You seem to agree that pictures look similar for RGB stripe and PenTile. Imaging scientists call these images bandwidth limited images. I would say that these look equivalent between RGB stripe and PenTile displays and can show this show this with MTF characterization plots.

One correction to what you said is that those of us at Nouvoyance never say that PenTile looks identical to RGB stripe. There are differences, but the differences that people point out are sometimes not correct.  For example, we render black and white text perfectly.
I know how tough it is to take a good photograph of a display, but even with the ones you show of very small, single and double stroke  black and white text prove that black and white text is not fuzzy, blurry, or otherwise defective. Look at the single pixel at the top of the “n”, where the curve joins the upright stem. You can see that black pixel every bit as well on the PenTile displays as on the RGB stripe. There is some softness at the edges of each of these that is attributable to the original anti-aliased font, which is also fully and faithfully rendered on the PenTile panels; so there should be no doubt that for black and white text it is rendering perfectly.

You say ”… edges which appear straight on a RGB stripe display will appear jagged, with odd pixels sticking out, just like on those old camera screens, and vertical lines will zig-zag across the screen.” I think that the photos you exhibited to prove this seem to prove the opposite. The same could be said for horizontal line edges on an RGB Stripe, as the red and blue subpixels appear so much more darker than the green. What makes it acceptable in either case is the fact that the resolution is chosen to be high enough that the subpixels blend together by the human eye, when viewed at the appropriate distance.

Let me add that much of the IP for PenTile is in our algorithms. There are several adaptive filters that look at many aspect of images and provide sharpening to edges, especially things like diagonal lines.
You pointed out that this image above demonstrates that the low res layout causes a grid artifact. There is, in fact, some graininess that is possible for a fully saturated green on a black background. The algorithms, for anything less than fully saturated colors, fills in the black regions with white or other color subpixels. This is the same as what is experience on an RGB stripe display that is fully saturated green on black, but in the PenTile case it appears as a checkerboard whereas on the RGB stripe it appears as green vertical stripes, albeit 30% closer together for stripe. Most people will be hard pressed to see this on a 300 dpi screen even at close range. This is especially the case since the human vision system has less resolution in the diagonals. It is also why photographic dot half tones have the same diagonal grid pattern.

As for your assessment that there is a diagonal organization to the display, I would agree, but I disagree with your conclusion. So, allow me to take it up a notch on the technical aspect of the answer. I would agree that the MTF of the display is less on the diagonal for the PenTile OLED RGBG panels than on the horizontal or vertical, but in all directions PenTile can write to the Nyquist limit. While the MTF of PenTile is slightly less than RGB stripe on the diagonal for fully saturated colors, it is still well in excess of the requirement of the VESA/IMID standard of 50% modulation, so it is not reasonable to downgrade the resolution by a factor of 1.4.  For the PenTile RGBW, the MTF, even in the diagonals, is the same as the RGB Stripe panel for black and white, that is to say, that they both will show a checkerboard pattern of equal modulation when the diagonal resolution limit is reached. The checkerboard is the result of an alias that occurs in the original data, before it reaches either display.

Let me turn to one other aspect of fitness for use, which is another name for good engineering, it is known to vision scientists that the human vision system is less capable of resolving detail on the diagonal than on the horizontal or vertical. So the slight fall-off in MTF on the diagonal nearly perfectly matches the sensitivity to detail on the diagonals. Any advantage of RGB stripe in this direction is often not seen, especially as we get into the resolution range of theis WQXGA panel.

So, I am troubled by calling the PenTile resolution claim “somewhat dishonest”. Samsung is saying that our WQXGA display is a PenTile RGBW LCD. And Nouvoyance is even directing those who are interested to our website, showing how it meets the industry standards for modulation contrast ratio when measuring Michelson contrast through a moving aperture grille. This is the test provided by the industry’s leading experts in display metrology. We have disclosed a great deal about what we do.

Do PenTile displays look the same as RGB stripe displays?

No, they look different in some special cases especially at the lower end of the resolution applications for  those with very good vision and well trained eyes, and, as stated above, with a bit more of a textured look for fully saturated green on black. At the higher end of the dpi range, e.g. products with 3.1” wVGA PenTile OLED, I have yet to see even one person who has blogged about a specific product about it looking grainy or less than sharp.

PenTile RGBW can look better than RGB stripe for things like the glint from metal and the reflections from water. It takes that white subpixel to give it that extra punch.

It is very important to apply PenTile to the resolutions where it makes sense – where pattern visibility is not visible for the bulk of the market. To us at Nouvoyance this seems to be good engineering for making a product that saves 40% of the power over the equivalent RGB stripe and meets the needs of the product. Surely, battery life and brightness are important engineering design parameters that as a package make it fit for use.

In the WQXGA product at 300 dpi in a product that is typically viewed from a greater distance in normal use than for a smartphone, so I am hard pressed to think that anyone will feel that this panel will look grainy or textured .

I hope to see you at SID to show you how good this panel can look.

Our Technology Demonstration at SID

For years, display makers have considered introducing field sequential color for TV applications. This technology doesn’t need any color filters, so it has great promise for very low power TV. The key issue has been an artifact known as “color breakup.” As viewers scan their eyes across the screen, it is possible to see colors separate. This is especially true for images such as black and white stripes.

For our prototype demonstration, we have collaborated with Samsung to develop PenTile RGBCW with FSC in order to demonstrate that color breakup can be almost entirely eliminated. And at the same time, it is possible to get extraordinary color gamut and very low power consumption through the use of RGB LEDs in a 2D dimming backlight. New algorithms allow us to smoothly stitch together FSC, PenTile RGBCW and the 2D RGB backlight to show what is possible for wide color and power savings of about 75% compared to legacy RGB stripe TVs.

If you’re going to be at Display Week 2011, you won’t want to miss this.