Kobo Glo light diffusion method?

[RoGuE_StreaK]

OK, a little left-field, but was just checking out some reviews of the Kobo Glo and wondered if anyone has any info / thoughts on how they have gotten such an even distribution of light from an LED side-lit film? Seems like it could be really useful for signs etc., kinda looks more like an EL panel.

 

[bshanahan14rulz]

pmma light guides and diffusing and diffracting films of varying degrees of diffusion and line widths. Open up a busted LCD and actually dismantle the screen part. You will find many different diffusion and diffraction gratings on top of the main light guide.

 

[RoGuE_StreaK]

Not disagreeing with you, but note that these aren't back-lit devices, they are e-ink rather than LCD; all light is apparently being applied to the front of the screen using LEDs at the edge (bottom) and side-lighting a film overlaying the screen? I'm sure there probably are various gratings etc., but the fact that they are getting an even distribution of light from what must be a very thin film only, without a screen-sized light guide behind it, seems pretty unique to me?

 

[bshanahan14rulz]

Ah, now that's a thinker! Standard light guides would end up distorting the image too much, you're right. It must be something more advanced and compact. This picture doesn't have a higher res, but might help us figure this out: http://ebookfriendly.com/wp-content...e-Touch-with-GlowLight-teardown-picture-8.jpg from here: http://ebookfriendly.com/2012/10/19/inside-nook-simple-touch-with-glowlight-pictures/#

They do say that in that particular model, the front glass, LEDs, and e-ink layer are fused together as one part. Don't know if they mean it's all modularized into one part, or if it is actually fused and not possible to tear down... I'm thinking it must be based on the light guides we see in LCDs, but since the optical source (LEDs, surface mount, uber-tiny) is much smaller than the usual ccfl, maybe they've been able to miniaturize it enough that it doesn't affect the display's readability too negatively

 

[RoGuE_StreaK]

The lighting on the Nook Simple Touch (the one in the teardown) seems nowhere near as good as the Kobo Glo's (or the Kindle Paperwhite), it's older and doesn't seem anywhere near as evenly distributed (from video reviews, eg: http://www.youtube.com/watch?v=MT1kin1xQEM), so I'm guessing the tech's a bit different. Haven't found a teardown of the Glo or Paperwhite yet.
edit: seems there's a video of a paperwhite teardown, but doesn't look at the screen at all. Love how these new release things are being torn apart and posted up, there's a whole deconstruction of an iphone 5 literally hours after it was released.

Anyway, if such a film can be made readily available for use in the future, I can foresee a lot of applications!

 

[ckc]

I just bought a Glo. ;)

when you tilt the reader, you can see 5 distinct sources on the bottom edge, and the entire top is slightly brighter then the middle

 

[RoGuE_StreaK]

Ha, here we go, Dave (EEVblog) has done a whole 30min teardown of the Paperwhite, he looks at the lighting from around the 10min mark:

Love this guy, he's like the Steve Irwin of electronics :D rather overly enthusiastic, but does a good job.

 

[bshanahan14rulz]

LEDs look like these almost: http://catalog.osram-os.com/catalogue/catalogue.do?favOid=0000000000022c6700090023&act=showBookmark

Placing bet that the film is probably made by 3m, but that's just a guess not based off of anything. Too bad he didn't disassemble the light diffusion layers. Good find, RS. EEVblog always has good vids :-)