Hacker News new | past | comments | ask | show | jobs | submit login
Using an LCD’s poor viewing angle to your advantage (chrisharrison.net)
308 points by dholowiski on Oct 24, 2011 | hide | past | web | favorite | 28 comments

I used to work at a place where our work product was kept in safes. They had these funky electronic locks, and instead of having notches on the dial there was a little LCD window on the top (facing the ceiling). Whereas most LCD manufactures try to get a wider viewing angle, the manufacturer had gone the other way, so you had to hold your head in exactly the right place or you couldn't see the numbers as you dialed the combination.

There was no way you could shoulder surf the combination. Even if you planted a camera the head of the person opening the safe would be in the way of the camera's sight line.

You can do that with any display. They are called privacy filters, you just stick them in front of the display and work exactly as you say.

More technically polarization filters. Laptop/Desktop manufacturers usually sell these at an obscene price, but there has to be a place to get them for a more reasonable price.

I wonder if this may have come a bit late to be useful - I can't see that colour inversion effect on my laptop monitor even at fairly extreme angles, so I'm not really confident that it's going to work on here. The advance in LCD technology may prevent this seeing any serious adoption, although I do think the "unread emails" one is pretty nifty. I'm not so sure about the banking one since I'm very unlikely to do any banking with someone sitting nearby, even if I knew a technology like that was in place.

There are still plenty of cheap LCDs in the world, they just don't show up in high quality products. I bought a cheap Android tablet (a Viewsonic gTablet) a while back to try out, and it had terrible viewing angles.

The banking example on the site actually implies designing an ATM specifically to take advantage of this feature. There are often people around you when you use an ATM.

Other products where security is an issue (special more-secure laptops?) could be designed this way as well. You wouldn't do banking with people watching, but if you needed the ability to do company work while, for example, spending a lot of time flying, it might be a net benefit.

You could have a MVA panel. They have superior viewing angles as compared to traditional TN panels, and from what I've seen their price is comprable.

This is a great example of the old engineering adage that you can turn every fault into a feature.

I thought that was an old jazz musician's adage ;-)

If you make a mistake, repeat it and call it your own arrangement.

The thing I find amazing is not so much that they were able to use colour refracting to overlay invisible messages on bad LCDs... it's looking at the problem in "creative-reversedness" (yes I just made that up).

We all would look at the limited viewing angle as a problem. Not enough people can see the TV, colour is bad, blah blah. But if we were to look at the problem in reverse - Too many people can see the screen from all angles, colour acuracy is not that important for all applications, and so on... we actually define a product that we can fit in the banking, HR, etc roles.

The next feat of genius was looking at what was causing the original problem and then leveraging it to create the new fuctional solution. Many just use the polar lenses, now you can just create a app that overlays invisible ink.

Great job.

Could this be used to correct my posture? I can just imagine my screen telling me to "sit up straight!" every time I slumped just like my father used to.

No, for that you just need PostureMinder:


This seems pretty cool. But is the viewing angle of an LCD an inherent property of the particular materials used or is it a side effect of uncertain manufacturing processes? I.e. could an LCD screen's viewing angle be changed if it was manufactured more precisely or calibrated better or something?

It's definitely dependent on the LCD monitor. I have a TN monitor, which works with the demo page, but on my IPS monitor, the text never really disappears from any angle.

Sorry what i meant was, even with the same brand and manufacturer, might there still be slight differences in viewing angle depending on how well each individual monitor was made/calibrated? My point being that, as cool as the idea is, mightn't it be impractical if you have to test/calibrate every monitor that's used, versus a manufacturing process that takes the usage into account from the beginning.

The works on even mac laptops

go to the demo page here: http://chrisharrison.net/projects/obliqueLCD/

look at your laptop screen from above and below (i.e., tilt or rock it) - not side to side.

More details here: http://chrisharrison.net/index.php/Research/ObliqueLCD

I could easily read all the text on that demo page, even when looking at my monitor head-on.

Turns out, the 'secret' text is coloured to blend in with a white background, but the page doesn't actually enforce a white background; my light-grey background doesn't provide enough contrast to read a novel, but it brings out the 'secret' text nicely.

This is definitely cool, but I still hate shitty LCDs. I bought 2 separate Samsungs that said they could pivot, but both (being made years apart) still had such horrid viewing angles that even looking straight on while vertical would make that distortion effect and make me feel sick.

I fought Samsung for false advertising using every method I could find and eventually they just gave me 2 24" IPS's and a 22" that can do 3D. The IPSs are really nice, but you can fry an egg on them they run so hot.

Using one of those shitty monitors if I get to the sweet spot where the text is invisible, if I move a hair up or down I can see the text :S

I wonder if this could be used for a game somehow...

In one example they have blurred the financial details on the screen from anyone viewing from the side.

I wonder if that could be iterated further such that all of the screen is blurred from the sides (presumably by dynamically altering the "overlay" to cancel out each color of each pixel).

This would then make a great alternative to a privacy screen for use on planes, etc.

Don't ATMs do something like this, or are they just built to have the shittiest viewing angles ever (which is obviously advantageous for this scenario)?

They have privacy filters, a separate covering that reduces the viewing angle of any screen to almost zero. You can buy one yourself, if you want.

That banking example would be better if the text viewed from an angle obscured the bank balances as well.

One of the later examples does that.

Currently, you can buy a private filter for any monitor and you can see what is in the monitor only if you are in front of it. I think they should develop their own devices with the applications to sale them.

Wow - I saw one of the monitors I currently use in their "Photos" section.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact