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LCD FTIR - first results
Posted: 27 November 2007 10:54 AM   [ Ignore ]   [ # 16 ]
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Could someone please run this through once more clearly stating as to what exactly Nima here has done?

Did He use the LCD as FTIR interface and align the IR LEDS to its sides?
And How did he light the LCD then?

Is this idea more viable using Rear illumination DI?

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Posted: 27 November 2007 11:30 AM   [ Ignore ]   [ # 17 ]
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Sounds good nima. Let us know how it goes. I’m also using that same casio projector for my projection table. It seems to work well =)

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Posted: 27 November 2007 10:57 PM   [ Ignore ]   [ # 18 ]
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chaitanyamuppala - 27 November 2007 10:54 AM

Could someone please run this through once more clearly stating as to what exactly Nima here has done?


Did He use the LCD as FTIR interface and align the IR LEDS to its sides?
And How did he light the LCD then?

Is this idea more viable using Rear illumination DI?

I made an FTIR acrylic board, but then removed the acrylic and left the LED’s.  You can not use rear illumination because of the diffuser for the LCD.

if you have problems, u should post images or detailed explainations for help

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Posted: 28 November 2007 12:15 AM   [ Ignore ]   [ # 19 ]
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So is it something like this?
[Attachment]

LEDS just above the lcd forming a thin layer or IR light above the LCD?

How does it react to ambient light?

Thank You For Your Patience....

EDIT: I Just Read Cerupcats PM after I Posted THis…

THANK You EveryBody… I seem To be Growing A brain Now…

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Posted: 28 November 2007 12:31 AM   [ Ignore ]   [ # 20 ]
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exactly;
i was using FTIR at first, then i removed the acrylic to wipe it clean or something, and realized it wasnt necessary, so i kept it off. (touching lcd glass feels a lot nicer than cheap acrylic, i just use the cloth that came with my ipod touch to wipe the screen and my ipod)

but this method works well if there are LED’s along all four sides of screen, because there is nothing now to trap the light, so the further away from the source, the more the IR light disperses.  Meaning on my prototype, the bottom edge of the screen gives more faint blobs than the ones at the top.  FTIR is more cost effective because you need only 1/4 of the LED’s.

but like i said, the FTIR or DI part is the easy part. if you still cant get distinguishable blobs, take a look at the layering of your LCD monitor.

‘cheaper’ LCD monitors will have fewer layers and generally work better.  for example, my samsung LCD monitor had 4 layers; a diffuser, a fresnel, a reflective polarizer, and another diffuser.  Whereas, the LG monitor im using, only has 2 layers, a diffuser and a fresnel.  So if your LCD layers has 4 layers or something, remove the reflective polarizer and the extra diffuser.

the flourescent lights give off IR, but because its reflected inside the acrylic block and the dots, it multiples, so line up IR blocking film along those edges which will cut down some of the stray IR light coming through.

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Posted: 28 November 2007 12:32 AM   [ Ignore ]   [ # 21 ]
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i dont quite understand your schematic but your description sounds clear

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Posted: 28 November 2007 12:36 AM   [ Ignore ]   [ # 22 ]
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Lol ... Im Half blind…

Thank You So much....

What about the ambient light…
And this would need the invert filter right?

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Posted: 28 November 2007 12:41 AM   [ Ignore ]   [ # 23 ]
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i dont think ambient light should misfire blobs.  The ambient source will need to be really bright and intensive.

im not using the latest version of touchlib, so i dont have the high-pass or invert filters (yet).  Just background subtraction and some rectify. but better filtering can only help.

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Posted: 28 November 2007 12:43 AM   [ Ignore ]   [ # 24 ]
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AH.... Thank You

PS: Im going to remove the Image I attached earlier…
because it seems to be slowing the page down…
causing lotsa inconvenience to everybody i presume…

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Posted: 28 November 2007 01:45 AM   [ Ignore ]   [ # 25 ]
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What do you think the frequency of LEDs should be for a 15” monitor [for the modified front illumination],

Im thinking 2 for every inch?

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Posted: 28 November 2007 04:59 AM   [ Ignore ]   [ # 26 ]
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Looks like someone surpassed me in the LCD FTIR development. Congratulations on that nice working screen. Mine will take some more time because I have lot’s of work to do for the university right now…

chaitanyamuppala - 28 November 2007 01:45 AM

What do you think the frequency of LEDs should be for a 15” monitor [for the modified front illumination],

Im thinking 2 for every inch?

If you want to know mine, I use about 42 leds for a 19 inch screen. Placed at both longest edges of the screen. But it highly depends on the LED frequency…

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Posted: 29 November 2007 04:30 AM   [ Ignore ]   [ # 27 ]
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nice stuff nima.... m waiting to get free from my current assignments and am dying to try out a LCD multitouch myself.... will bug you when m at it smile

cheers

keep up the great work!!!

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cheers!!!

deej
http://therealdesktop.blogspot.com

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Posted: 29 November 2007 09:43 AM   [ Ignore ]   [ # 28 ]
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Is it necessary to have leds on all edges for a ftir lcd?  I have tried di and got great results (not with an lcd, normal projection method).  I have been taking apart my 15 inch lcd and have been running into problems as to what to keep or lose.  I know that for every lcd it is different as to what components should be kept or not.

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Cheers Mate

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Posted: 07 December 2007 02:34 PM   [ Ignore ]   [ # 29 ]
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Nima!  looks amazing man, Great work.  I have been trying to build my own, attached a diagram of what i am thinking.  sounds just like yours.  but the IR sensors are Above the plexi glass(i like the feel of the plexi opposed to the lcd screen) instead of of shining threw the middle.  the IR film is just bordering of course.  but i have a 24 inch wide screen LCD that i would love to take apart and make it a table system, how far away did your camera have to be under it?

Thanks!

and again great work!

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Posted: 09 December 2007 01:13 AM   [ Ignore ]   [ # 30 ]
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Sorry everybody but I’m not entirely sure as to how nima’s setup is. According to what I have read, he is using IR LEDs on top of the LCD in a front illumination setup?

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