E-paper display reaches the realm of LCD screens
spectrum.ieee.org613 points by rbanffy 4 days ago
613 points by rbanffy 4 days ago
Eink always could be driven quickly. The issue is that LCDs are more powerful efficient at high refresh rates
EInk needs a lot of power to move the heavier ink particles around. If you are doing that more and more rapidly, then even more power is drawn.
By 75Hz, I'm almost certain that LCD is far more power efficient. The LCD pixel (aka the liquid crystal) is a glorified capacitor, it takes some power to charge but it's exceptionally 'light' compared to eink.
That's why LCDs can go faster and faster. It's just physics. A capacitor / twisted crystal uses less power to turn on or off than EInk.
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EInks advantage is that if you turn off power, the ink stays put. So you spend a ton of power moving the ink around and then save lots and lots of power over the next seconds, minutes or more.
That's why EInk is ideal for once-a-day updates of prices (or other retailer tasks). The less you update, the less power used.
Our driver board, under continuous use, draws about 1 to 1.5W. A recent article below goes into some detail about our design choices.
https://www.crowdsupply.com/modos-tech/modos-paper-monitor/u...
Thanks. That article seems to have the quote I was looking for.
> E-ink screens are quite power hungry when it comes to peak current. Modern high-resolution panels can consume >20 W peak.
This is where I was wondering and yeah, 20+W is pretty hefty to support a relatively small 8" EInk screen or something.
All those updates cost all that power as long as updates are occurring. Maybe you can optimize many of them away (if some parts of the screen don't move, especially if software was rewritten to optimize for the display).
More importantly, it sounds like you've created a full custom FPGA controller over the voltages that go into an EInk display? That's impressive in its own right even if I don't think 75Hz is a good idea lol.
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FPGA or Full Blown Microprocessor are the only choices here. A high power SIMD/NEON arm64 probably could do the job, but I think the Spartan6 is a good choice as well and has more obvious and straightforward parallelism (and probably all the pins required to control the screen. Even a big microprocessor won't have as many low latency pins as an FPGA).
> Maybe you can optimize many of them away (if some parts of the screen don't move, especially if software was rewritten to optimize for the display).
Yes, that’s definitely something we want to work toward. As the community grows, we hope to tackle these kinds of optimizations together.
> A high power SIMD/NEON arm64 probably could do the job, but I think the Spartan6 is a good choice as well and has more obvious and straightforward parallelism
Yes, precisely for the reasons you stated. We also talk more about it below:
- https://www.youtube.com/live/okjJURIejIY
- https://github.com/Modos-Labs/Glider?tab=readme-ov-file#desi...
Congrats on the article either way!! I'm one of the daylight founders so I love to see progress made on electrophoresis
We personally couldn't make it work with low power but this seems promising!
Would be cool to get an actual desktop screen with something like your screen tech.
The article says:
> “Traditionally, the [e-paper display] controller used a single-state machine to control the entire panel, with only two states: static and updating,” says Modos cofounder Wenting Zhang. “Caster treats each pixel individually rather than as a whole panel, which allows localized control on the pixels.”
So in practice would it ever actually hit 20W unless you're doing something that requires constantly updating the whole screen, like playing a video game or watching a video? Surely updating only a few pixels at a time can't be that power hungry, right?
You guys should do a collab with the framework people. I bet they'd be happy to offer an e-ink screen on their laptops just as an option. I've been waiting on an e-ink option for ages.
We’d like to offer a kit for the MNT Reform, and possibly the Framework, in the future, though it’s not part of our current roadmap.
This...would be insanely amazing. A _real_ laptop with a proper 13" eink display at 75Hz!
I’d gladly pay for a crappy 30Hz version literally right now if they sold that. A framework with e-ink sounds like a dream
E-Ink's other advantage is being a non-emissive display. Transflective LCD displays have low contrast. I'm literally holding an e-ink tablet over the transflective monitor I'm typing this on and the difference in contrast at the same ambient illumination is considerable. If the price were right, I'd definitely consider a 75 Hz e-ink monitor even if the power draw was more than a normal LCD monitor.
Transflective LCD is bad but e-ink has terrible contrast compared to normal LCD displays. Like 4:1 vs 1000:1.
Maybe, but LCD panels are a light source, so it's not apples-to-apples. I _perceive_ eink as higher contrast than any LCD.
That is odd as I definitely do not perceive that.
My Kindle has much less contrast than my iPad, phone or computer - albeit I have brightness turned up.
I only use the Kindle as its battery will last over a day if reading my iPhone will not and also if reading in bright sunlight.
That depends on the external illumination. LCD contrast goes to shit under bright light.
In my experience using e-ink readers (admittedly I have a Kobo, which may not be the state of the art), I would like to refresh the screen rapidly in bursts -navigating menus, flipping past an index - and then have a non-backlit screen with low power cost to show the same content for a while. In other words, a variable refresh rate.
If you think of the refresh rate not as a constant frequency but as variable with user input, there are some cases where driving eink quickly in short bursts could make sense? It seems like this project offers a foundation for such a controller, where e-reader controllers are strictly optimizing for low refresh rates. E-ink is not going to be competitive for playing a video game or watching a video, but you can create a more responsive experience with less eye strain for typical tasks like marking up documents.
Yes, that’s the mental model I’ve been working from. Variable refresh tied to user input makes a lot of sense: short bursts of speed for navigation or editing, then settling into a low-power static state.
Part of the challenge is deciding what belongs in hardware and what should sit higher up in the OS or software stack.
Hopefully, as more people get the kits and the community grows, we’ll be able to think through these questions together and explore where the right balance between hardware and software should be.
That sounds like the way to go. In terms of reading books (my normal usage of e-ink readers) you don't need 60hz when flipping a page, but it's a must when trying to use an app menu, or using Google Drive for example.
Identifying when to increase the refresh rate may be a challenge but I can see it pretty doable for this kind of "limited" scenarios where you either read or navigate a storage app.
> EInks advantage is that if you turn off power, the ink stays put.
E-ink's other advantage is that it reads like paper. In a desktop context I could not possibly care less about the power consumption, but being able to read a forum thread, chat channel, HN discussion, etc. without a backlight would make my eyes very happy.
It's also about being usable in the sun.
Whereas it may be used in outdoors-like natural lighting, it is not (always) true that it is "usable in the sun". On one such product¹ there's this "Important Notice" advising users to "avoid exposing the E-ink screen to direct sunlight or intense ultraviolet rays, as this may cause irreversible damage to the screen."
¹ https://shop.dasung.com/products/dasung-25-3-e-ink-monitor-p...
there's no evidence/meta-analysis pointing e-ink screen tiring eyes more/less than LCD
There's no evidence/meta-analysis pointing milky and a warm blanket is cozier than water and a sleeping bag.
Is there any actual scientific study saying anything either way?
I'm aware of a lot of anecdotal evidence in favor of e-ink displays being easier on the eyes than normal LCDs in some way, my own personal experience included, but I will happily admit I'm wrong if there are studies indicating otherwise.
I like my Kindle and DIY e-ink weather display but I'm not religious about it. I wouldn't be shocked to find out it was just a weird placebo thing because it's different.
i don't think there are much but i made my research a decade ago after realizing i was having a good time with my smartphone compared to my e-reader
[1] suggests that LCD even increases processing speed compared to e-ink
[0] https://pubmed.ncbi.nlm.nih.gov/22762257/
[1] https://bop.unibe.ch/JEMR/article/view/2338/3534
there's a study from Havard concluding "e-ink is 3 times better for eye health than LCD" but it feels rather dubious from the claims (blue light stressing more the retina... like i couldn't use a glass or apply a filter on my screen), light intensity (again...), in-vitro study and who funded the study (a great e-ink screen producer) -> https://sid.onlinelibrary.wiley.com/doi/10.1002/jsid.1191
i probably read hundred books since i sold my e-reader and moved to my smartphone. i really like having a single device. battery is fine. physical books with images still rocks but maybe becuse i don't have a tablet :)
I've spent thousands of hours (I think) reading on a phone. I even prefer it over a physical book because it doesn't have that annoying crease and it doesn't spoil the story by telling me how far along in the book I am.
Well, not sure about your eyes, but you are certainly inviting neck problems, and carpal tunnel syndrome.
The problem is that there's not even a hypothesis for how light reflecting off an e-ink display could be easier on the eyes than light emitted from an LCD, unless the LCD is using PWM dimming of the backlight and thus flickering. I've never seen a claim that e-ink displays are easier on the eyes get further than the most obvious question: have you tried e-ink and LCD at the same brightness and similar color temperature?
How would that comparison work using an e-ink display illuminated only with ambient light in the room?
(i.e. setting the "frontlight" brightness to 0% on a Kindle, which would also eliminate color temperature control other than room ambient light).
It does seem hard to believe that e-ink + a reflected frontlight would be any easier on the eyes than an LCD backlight (particularly since it's probably also using PWM). But an e-ink display on its own at least removes an additional light source pointing directly at the eyes, which could provide a potential mechanism for different effects on the eyes/brain.
> But an e-ink display on its own at least removes an additional light source pointing directly at the eyes, which could provide a potential mechanism for different effects on the eyes/brain.
Not really, since LCD/OLED aren't an additional light source, but absorb and thus replace the ambient light that would be coming from their direction.
I don't know the science, but my experience is that my brain is simply able to process and retain information so much better with eInk than with LCD screens.
I started as a teenager with cathodic tubes, which were killing my eyes and bringing daily headaches; moved on to LCDs which stopped the headaches but still tire my eyes significantly (some of them literally make me cry after a few minutes); and then found eInk and it's so much better, I will definitely move to that once prices of large color monitors at 60hz get into my price range. I honestly don't care about power draw one bit.
Not really, since it's not just about the light intensity, but also its spectral power distribution. This especially matters when using the display in a darker environment with low-temperature illumination, e.g. when reading before bed.
Quick experiment to show the effect: Go into a room with low 2700K or lower-temp lighting. Take an LCD, set its colour temperature same as the external lighting, then display an all-black screen. Since the screen is displaying #000, the software colour temp adjustment can't do anything, and you'll see the screen as emitting blue light, the colour of its backlight.
OLEDs don't have this issue, which makes them great for night-time use when configured properly, but they also generally use low-frequency PWM dimming on low brightness.