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Ideas for my next DSI project / Object Recognition + LCD (LED) TV
Posted: 06 May 2010 09:46 AM   [ Ignore ]   [ # 31 ]
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That were also my thoughts. When i have enough time i will try that with some reflective foil i have lying around

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Posted: 28 May 2010 09:16 PM   [ Ignore ]   [ # 32 ]
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Payne have you tried either one of these as diffusers?

http://www.acrylite-shop.com/US/us/acrylite-satin-ice-8ww9w0k5tzz/acrylite-satin-ice-colorless-0d010-df-iwywkzla8w7~p.html

http://www.acrylite-shop.com/US/us/acrylite-crystal-ice-ebu6h21c4k/acrylite-crystal-ice-colorless-0m001-sc-kcshdt6ngvj~p.html

Also how does the Rosco 220 compare to regular Vellum?

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Posted: 29 May 2010 01:17 AM   [ Ignore ]   [ # 33 ]
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sorry, I haven’t tried any acrylite sheet but i think that they are like frosted glas and therefore i think they have too much distortion but thats only a guess.
Compared to regular Vellum the foil has less distortion of the camera image, so its better for fiducials.

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Posted: 05 June 2010 04:31 PM   [ Ignore ]   [ # 34 ]
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Hey guys, I’m very new to it and I’ve noticed that u are kinda struggling with backlight, how about using some photography lamps etc etc? Wouldn’t they do the trick? Or is it has to be led....

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Posted: 05 June 2010 06:36 PM   [ Ignore ]   [ # 35 ]
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the amount of light is not a problem but the even illumination of the lcd.
If you want to use lcd and fiducials you should use a weak diffuser or no diffuser at all so its not easy to get an even backlight illumination for the lcd.

The lamps u mentioned would be possible, but still the same problem of uneven illumination.
LED illumination is better in this case cause you can make an edge-lit lcd panel with a sheet of endlighten.
Also white leds normally emit no ir or far less than normal bulbs.

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Posted: 07 September 2010 11:49 AM   [ Ignore ]   [ # 36 ]
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perhaps a sheet of enlightened underneath the LCD with white LED around it. If its not enough power to illuminate your screen, then continue to use your old backlight but put the diffuser on that?

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Posted: 07 September 2010 12:39 PM   [ Ignore ]   [ # 37 ]
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Already tried endlighten but you loose quite a lot of light. I now made a custom backlight with a transluzent backlighting acryllic and covered the inside of my table with sheets of wood (like a box inside a box^^) which i spray painted with high glossy white on the inside,
I also placed my 4 cameras behind the backlight and drilled some small holes in so that the lens can look through.
Works like a charm wink

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Posted: 07 September 2010 01:10 PM   [ Ignore ]   [ # 38 ]
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im intrigued payne86 got pics of this backlight setup......is your LCD now transparent?....perhaps a you can show me you layers

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Posted: 07 September 2010 01:13 PM   [ Ignore ]   [ # 39 ]
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cottonwood00 - 07 September 2010 11:49 AM

perhaps a sheet of enlightened underneath the LCD with white LED around it. If its not enough power to illuminate your screen, then continue to use your old backlight but put the diffuser on that?

Hi, about time to chime in on this thread.

I’ve built a 42” DSI LCD (my second table) setup which can read FID’s, fingers and objects (thanks Amit) just fine.  I’m not using the diffuser anywhere near the LCD.  So the system is able to “see” through the LCD without any difficulty. 

The setup is like this:

EndLighten XL (IR) ==========
LCD and spacers ------------------
EndLighten XL (BL) ==========

Distance between screen and camera can vary depending on your camera array.  Currently I test with one camera but the tech is solid for as many as you can stitch together.

LCD/LED Backlight ==========

The backlight (BL) in this build is two fold.  One is a support sheet of EndLighten edge lit with White LED’s.  This creates a nice even, somewhat dim visibly diffuse, light condition.  I use this instead of a diffuser for both added illumination and to prevent the obvious transparency that an LCD setup without a diffuser suffers from.

The second Backlight is the one pulled directly from the LCD Screen itself with all of it’s diffuser layers intact.  I mount the camera for my current build into the lower backlight so only the size of the lens is an issue for interrupting illumination.

The combination is surprisingly successful. 

I’ll post more detail on the build after I take some photos tonight or tomorrow.

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Posted: 07 September 2010 01:35 PM   [ Ignore ]   [ # 40 ]
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cottonwood00 - 07 September 2010 01:10 PM

im intrigued payne86 got pics of this backlight setup......is your LCD now transparent?....perhaps a you can show me you layers

I’m currently not at home, will make photos later but i attached a quick drawing of my setup.

The layering is as follows, from TOP to BOTTOM:

-Endlighten(IR)
-LCD
-very weak diffuser
-light box (painted white)
-trueLED Plexiglass (Special cheap acryllic for led Backlighting) with 4 holes for the camera lenses
-Bottom of the light box with led strips attached to it like an array and camera mounting (also painted high glossy white)

@grimjack2600:

Nice idea to replace the diffuser with a sheet of endlighten, maybe i’m going to try that one.
Can you see the inside of your box if you look straight down trough the LCD ?
That was the problem in my setup for a long time and the reason why i used the weak diffuser sheet.
Can’t wait for the pics =)

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Posted: 07 September 2010 01:49 PM   [ Ignore ]   [ # 41 ]
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payne86 - 07 September 2010 01:35 PM

cottonwood00 - 07 September 2010 01:10 PM

Can you see the inside of your box if you look straight down trough the LCD ?

Not really, I’ll post some pics this evening time permitting.  Just got back from PAX yesterday and the family would like some of my time to be _away_ from the tables smile.

I dig your bottom backlight design.  Can you give more details about the materials and the layout? 

I’m currently using a CFL backlight in which I’ve placed my camera between the elements and below the diffuser layer with a hole punched in the diffuser for the lens.

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Posted: 07 September 2010 02:04 PM   [ Ignore ]   [ # 42 ]
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cottonwood00 - 07 September 2010 01:10 PM


Not really, I’ll post some pics this evening time permitting.  Just got back from PAX yesterday and the family would like some of my time to be _away_ from the tables smile.

I dig your bottom backlight design.  Can you give more details about the materials and the layout? 

I’m currently using a CFL backlight in which I’ve placed my camera between the elements and below the diffuser layer with a hole punched in the diffuser for the lens.

I’m going to make some pics, and explain it further but its similar to what you did.
I placed about 5 meter of led strips on the bottom of the box, arranged in lines next to each other and placed the four cams in between them.
On top the special backlighting acryllic which acts like a diffuser and spreads the light from the leds evenly (also with holes for the lenses)
So pretty much the same as you did with the CCFL backlighting. i then made some kind of light tunnel from the backlight up to the lcd which i painted glossy white.
it reflects some of the backlight and gives some extra illumination on the lcd panel and you get a nicely lit white background for the lcd.
the weak diffuser right underneath the lcd is used only to prevent you from seeign the lenses of the cameras looking trough on the bottom of the light box.

The setup works quite well with fiducials, although not perfect because of the diffuser sheet under the lcd.
I also switched to 4 cams recently cause with a wide angle lens its nearly impossible to track fiducialson my table.

how high is your table? Did u use a wide angle lens? Which camera did u use?

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Posted: 07 September 2010 03:06 PM   [ Ignore ]   [ # 43 ]
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Oh, hey, your the one with the cool light cone right? 

Currently I’m just using a PS3 cam to get things organized.  I just ordered my Firefly MVU today.  So hopefully I’ll have it by the end of the week.  Yes, currently I’m using a wide-angle lens and I’ve got approximately a 16” deck (internal dimension) between the screen and the backlight.  This distance is not calculated but instead just what I happened to have already setup.  My first table build is a rear projection setup which I took the innards and put into a new case.  When I finished building the new LCD screen I just stuffed everything into the old case without modification and it happened to work.  Very scientific, I know.

I’ll actually be refining the “build” this weekend I hope.  Adding a bottom and some supports to get it off of the ground.

Currently I’m using heavy weight velum inside the housing for my “white” reflective interior.  This works really well as it gives a diffused reflection while also staying very white.  A very slightly textured interior has the advantage of scattering light to create even illumination.

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Posted: 07 September 2010 04:18 PM   [ Ignore ]   [ # 44 ]
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grimjack2600 - 07 September 2010 03:06 PM

Oh, hey, your the one with the cool light cone right? 

Nope, but i saw that one too wink Can’t remember who it was but nice idea.

So i see you have pretty much the same setup as i have, except the size of the screen and the materials used for reflective interior and of course your “endlighten diffuser”
I used wood which i spray painted white and after that a second clear coating to make it more reflective. It also has some sort of micro bumpy texture because of the wood i used but that just happend accidentally xD

I definitely have to try that endlighten thingy instead of my diffuser. If that works, fiducial tracking would be much better with a single cam.
BTW how well does your setup track fiducials? As i said, i didn’t get very satisfying results with a single cam + wide angle.
Four cams work pretty well.

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Posted: 08 September 2010 08:57 PM   [ Ignore ]   [ # 45 ]
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yeah side angle will distort you picture alot, I think the enlightened diffuser is the way to go for LCD fudicials for sure. It might not give the best lighting but you can always add more below and then diffuse it below the camera. I’m going to have to add that to my design.

Grimjack im interested in your fiducial tracking as well, got any vids or tips?

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