Yann Vernier’s Blog

2010-10-22

Around the corner – displays

Filed under: Uncategorized — yannv @ 18:26

I recently posted that I’ve ordered a so called E-reader. The particular features about that are all in the display; it needs to be readable in sunlight, and consume little power. That’s why the one I picked has an E-ink display. But as is the tendency of such things, there’s alwyas something better just around the corner – something not yet available on the market, or still just a bit too expensive. This post is a collection of the (hopefully) emerging display technologies I know of, with a focus on E-reader style displays.

E-ink

I know, not really emerging when I’ve already ordered a third generation device, is it? Still, these deserve mention at least as a point of reference. The e-ink displays are purely reflective and stable, meaning any energy to display the image comes from light bouncing off it. Changing images, on the other hand, is a lengthy process frequently involving multiple passes (at least for grayscale). New driving chips has reduced this, but it’s still suffering from flashes to black and white. E-ink Triton was recently announced, and will add color capability.

SiPix

Also on the market, and near identical to E-ink displays, SiPix claim to be the biggest in electronic paper modules. This is probably because they make custom models, only capable of showing specific segments. They do make active pixel matrix models as well.

Nemoptic Binem

This was the type I was mostly convinced to wait for. Of course, only days later the company went bankrupt, and I made my compromise. So what was so good about Binem? It came down to a few properties: Manufacturing technology as common TFTs, translucent bistable layer so it could be combined and backlit (demonstrated with OLED), and updates at video speeds without any flashing whatsoever. We never got to see what the cost might be, and I boggle at a world where this company could find investors hard to convince.

Pixel Qi

An active contender is the Pixel Qi displays. I’ve been wishing for one of these a long time, since they’re both full speed displays and feature a reflective mode. They’re proven technology, being a spin off from the OLPC project, yet they’re barely beginning to inch into the market. Currently they’ve launched a DIY kit for a few netbook computers, and we’ve heard of one tablet device that should have a Pixel Qi display. A peculiarity is that the display goes nigh monochrome when passive, which makes the subpixels more interesting for spatial separation, but this will only triple the resolution along one axis. I’d have considered making a non-square color pixel ratio to exploit the higher resolution better – video formats drop the color resolution anyway.

Mirasol

Probably the most promising development among passive displays, Mirasol uses the very property of light wavelengths to accomplish color. Not only that, it’s a bistable technology with very fast updates – although not yet at common video levels. This might have gotten me to wait, as there are now rumors that there’ll be an e-reader with their technology next year. Unanswered questions include what sort of resolution they’ve accomplished, as they’re literally bilevel and will require more subpixels per pixel to get gradual levels. On the plus side, this means they’ll be working on getting the resolution much higher than the intended pixel density, and I’m a sucker for true resolution. Let’s hope the controllers will exploit it.

Unipixel

This display is neither stable nor passive. Unipixel displays are pure active matrix, like today’s common TFTs, but operate with very rapid shutters. The idea is to perform like some color scanners, flashing whatever color base you need through the shutters (typically red, green and blue). This requires basically a distributed PWM controller, fast enough to give the desired color precision and wide enough to handle every pixel at once. It’s been done for OLEDs, but there you have the convenience to be the last visible layer. Basically it’s like a flat panel version of a DLP. The advantages of this method are that each pixel is placed in the same spot (no shifted subpixels), the shutter can pass more of the light than common panels, and since it starts with being fast there’ll be no ghosting. It’s interesting, but hardly the stuff to compete with stable displays on energy efficiency.

OLED

Another technology neither stable nor passive, but included for comparison. OLEDs use directly shining subpixels, which makes them very energy efficient for an active display; there simply is no backlight to be filtered. But it does suffer from the fact that all the picture detail has to be emitted from electrical power, meaning it’s impractical to compete with sunlight.

TFTs

A few of these are used as e-readers. TFTs are divided into a few different technologies, and the Pixel Qi display actually belongs to this group – but most of the modern ones are limited to backlit operation. The legibility when the backlight is turned off is normally negligible. Apple’s iPhone and iPad displays are of the IPS type, which have better colors and viewing angles than most – I got an IPS panel for my stationary display. The cheap panels tend to be of TN type, which has horrid viewing angles – color tends to go nuts as soon as the angle is a bit off. This is what most laptops and TVs use, and you’ve surely seen the result when you tilt the screen just a little wrong. The same effect occurs when you get close – and since it differs for horizontal and vertical angles, you can’t expect decent performance if you turn to portrait mode. And to make matters worse, a lot of displays are built glossy or shiny. Great if you need a mirror, but that’s not the purpose of my displays.

CPT

A direct competitor to Pixel Qi, CPT have a sunlight readable display that doesn’t lose color quite as much when lit strongly from the front. I don’t know much more, as all I’ve seen are a few quick video clip of a fair booth, from netbook news.

I’m sure I’ve missed a few interesting ones. Please let me know which!

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2010-10-20

E-book reader

Filed under: Gadgets — yannv @ 19:46

My gadget mania has struck again. As is my habit, I again selected basically the most expensive device on the market of some particular type. It started, pretty much, with finding a version 2 Kindle in a friend’s sofa. Neat device, I thought, and fiddled about with it for a while. It was tempting, but there are a few things I don’t like about the Kindle.

  1. Amazon control the device, not I. Sure, they have less control if I never go online with it, but half the point of a Kindle is their free data service.
  2. The resolution is too low. I read many technical documents, where 600×800 is just slightly too small to be practical.
  3. The contrast was just slightly disappointing. Not a showstopper, but annoying.

Still, I just couldn’t get the idea out of my mind – so I started looking about for alternatives. MobileRead hosts a wiki with a rather helpful overview. Turns out, there were a whole slew of promising demonstrations. Kindle DX exists, but has the same control issues and notably higher cost. Irex has closed. Nemoptic apparently went bankrupt. Brother SV-70 is apparently only for the Japanese market and only their own proprietary format. The Skiff reader had a clear advantage in resolution, but the whole company was swallowed by News Corporation (as yet not to be seen again) before release.

Somewhere along the line, the old idea that a stylus for handwriting would be nice resurfaced. The trigger this time was reading about the Onyx Boox, but for a measure of how far back the concept has interested me, I have an RS-232 connected inductive digitizer from Genius. It’s old, and not very flashy, but does work – although the last time I used it I had to patch the driver to work with recent Xorg. I’ve tried a few touchscreen devices since, such as the TuxScreen, Palm III, and Agenda VR3. There’s an important side effect of the most popular technologies (capacitive and resistive) – glare and reduced contrast, the very things the e-ink needs to avoid. The Boox 60 didn’t have a particular problem with this, because the inductive digitizers can be placed behind the screen. The downside is that a specific stylus is required, so these aren’t touch screens (apparently that’s what you have to call it nowadays to sell), but it makes up for it with higher precision and, again, no extra layer in front of the screen.

There’s one concern I haven’t yet mentioned. I’m a programmer, and like tinkering with all my gadgets to some degree. I absolutely loathe it when the manufacturer takes effort to destroy this option (hello, Sony), but if they elect to be helpful, that matters to me. One brand stuck out in this regard, a Ukrainian developer called Pocketbook. They have released SDKs and sources, and significantly, showed active efforts to maintain and enhance the firmware for existing models. The developer site, hosted at sourceforge, was filled with Russian discussion, but they are currently expanding – with offices all over the place, and a multilingual bookstore. They’re about to launch a few new models, and the top of the line – Pocketbook Pro 903 – is what I’ve ordered. The deal closer, really, was seeing no less than three active and helpful representatives on the mobileread forums.

So how well did this model stack up to my feature wishes?

  • Active updates from Pocketbook, flexibly overridable firmware, and an active developer community – they do have a DRM thingy, but they point out themselves that’s only because publishers demanded it. Control: Good enough.
  • Resolution: Turns out the nicer options (1600×1200) aren’t anywhere to be found. The 903 has the top E-ink model, at 825×1200 – same size as Kindle DX.
  • Contrast is, rumours have it, slightly worse than the new Kindles (“Pearl” is apparently the cream of the crop) but better than earlier generations, as the one I tried. It will suffice.
  • Inductive digitizer makes navigation easier and scribbles possible, without sacrificing legibility.
  • Connectivity is just overkill – Bluetooth, 3G+GPRS, WLAN. This thing can connect through my cellphone if its own SIM won’t do.
  • Memory is not shabby – 256MiB RAM, 2GB built-in flash, and a micro-SD slot for expansion, upgrades or experiments.

There are other details, such as a frankly impressive PDF reflow feature, but thus far it’s enough to excite me. Certainly there’s silliness about too, such as the “Pro” moniker present on all the new Pocketbook E-ink readers. By the way, the 603 model has the exact same features with a smaller screen, and the 902/602 differ by dropping 3G and the digitizer. All of them should run the same software, including all the add-ons.

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