New Material For Fast-Change Sunglasses, Data Storage

sciencehabit writes "'Researchers have developed a material that almost instantaneously (30 ms) changes from clear to dark blue when exposed to ultraviolet light, and it just as quickly reverts to clear when the light is turned off. The new material, one of a class called photochromics, could be useful in optical data storage as well as in super-fancy sunglasses.'" A comment to the article notes some of the potential dangers of quick-change sunglasses.

flicker probably not an issue

[boog3r]

(not sure why i posted this on their website. i blame the booze).

Did a bit of math and figured out that at 60mph you would need a complete obstruction every 2.5 feet to induce a state change (on-off), 5 feet for a full flicker (on-off-on).

This compound cycles on-off 33.333 (repeating, of course) times/sec. Halve that for a full on-off-on cycle. The human eye can do fine with a video frame rate of 30/sec, but can detect up to 72 frames/sec.

It is possible the flicker may induce optical illusions, but not likely considering the optimal cycle time produces the highest flicker rate. Any UV transition slower will produce less flickers/sec, while a faster transition will create an increasingly static tint (chemical can't transition quickly enough).

Now sitting under a 60Hz black light, that may be kind of trippy.

Re:But is the reverse reaction temperature sensiti

[tresstatus]

I believe you are totally missing the point for the light sensitive glasses. they are never meant to be sunglasses. they are meant to protect your eyes from UV rays so that you don't damage your eyes. they also only barely darken anything you are looking at, with it being most noticeable on white things, like clouds or sheets of paper. what they really excel at is taking the edge off when you are looking at an object that is extremely bright........ EXCEPT FOR THE SUN. you aren't supposed to stare at the sun while you wear these.

I wear glasses that have the newest version of the transitions lenses. they turn much faster in heat than they do in cold... just the opposite of the older version. even still, when i wear them, i can't tell that they've changed to dark until I take them off and look at them.

my advice is that if you want your prescription glasses to work on the beach, you have 3 options: buy prescription sunglasses, buy a style of sunglasses that comes with a built-in clip-on (usually magnetic), or get contacts and wear regular sunglasses.

Re:Blue, non-polarized, non car = whatever

[miggyb]

Isn't that exactly how LCDs work? When no charge is applied to a liquid crystal, it lets light through, but when there's an electrical charge, it becomes dark. All you'd really need is a pair of glasses with a battery, photodetector, and two monochromatic LCD cells the size of the actual lens. I don't think it'd be that much of a pain in the ass to have to recharge your glasses at night.

Re:What's new?

[pereric]

Maybe that it doesn't need external power or control. IIRC, the auto-dim welding helmets I know of need an external power source (small solar panel + battery I presume), and dims by applying a current to the glass. I was also going to ask if this could be used for a simpler welding mask, but 30 ms is perhaps too slow for protecting against the lots of UV arc welding produces.

Re:flicker probably not an issue

[dintlu]

This is not true. Sunburns are caused by UV rays.

http://en.wikipedia.org/wiki/Sunburn#Cause [wikipedia.org]

Re:Blue, non-polarized, non car = whatever

[fahrbot-bot]

Yet, there is no way to have changing, polarized lenses (right now).

Although this won't help inside a car (as the windshield blocks UV), Transitions lenses can be polarized. As an alternative, they also offer Drivewear [drivewearlens.com] lenses that are polarized and respond to both visible light (less darking) and UV light (more darking). These are also available from Oakley [oakley.com].

Re:The eye adapts slowly

[blincoln]

That's the problem with this and every other UV adaptive lens treatment: Glass (like, for example, your windscreen) blocks UV.
So, they don't actually work when you're driving.

Glass doesn't fully block UV. I take UV photos using regular glass lenses with a UV-A bandpass filter in front. I lose something like 3-4 stops of light sensitivity compared to visible, but at least some of that is probably due to the camera sensor not being designed with UV in mind.

Apparently glass does block UV-B, UV-C, and shorter wavelengths. My camera isn't sensitive to wavelengths shorter than UV-A or I'd test it myself.

Re:Only ultraviolet? So they are almost useless

[rockNme2349]

They are activated by ultraviolet light...

Since they turn dark blue, I'll let you figure out what type of light they filter out.

Re:But is the reverse reaction temperature sensiti

[An ominous Cow art]

I've been wearing glasses with photogrey lenses since I was about 8, so 35 years or so. I've never noticed a problem with them failing to darken in hot weather.

Larry

Re:epileptics-need-not-apply. Why not?

[maroberts]

I don't have a sister. Wait a minute, whose bed is this? There's someone behind me... Damn, my glasses have gone dark, can't see a thing.

Re:flicker probably not an issue

[Bigjeff5]

It filters UV-B and UV-C pretty well, but not UV-A. Phototropic glasses are usually less effective in a car, but not completely useless.

Depending on the wavelength it changes at, these sunglasses could either work great or piss poor. Should be interesting.

Re:Slow Memory

[BitZtream]

Which is exactly what todays 48x burners and hard drives already do.

I wish people would realize that hardly anything in a modern computer is done serially anymore. Flash drives, standard hard drives, CD/DVD drives, all of them read/write multiple blocks at once to improve throughput without actually doing anything physically faster.