Hi i am new o the forum but i have been reading up for about a week. Now i am ready to jump into my own project, however i want to go about things a bit differently. I want to use a 22” LCD and remove all the housing and back lit, making the LCD transparent. I have searched a lot but have not found anything about this. After i get the LCD transparent, i would insert the acrylic above the LCD, and light the LCD with a HID light. Look at the images below. I would like to hear what you guys think.

I’m not sure I understand what you are after.  What’s a HID light?  You are using internally lit acrylic, correct?  Does a HID light emit IR?

Using an LCD sounds like a sweet idea, but it will make you a lot more susceptable to environmental factors.  You won’t have a compliant surface to dampen ambient light, so if there’s a bright light within the view of your camera it will make finger tracking a lot harder.

If you use a projection setup, you can use the compliant surface & projection surface to block out ambient light.

a possible solution to that TIF is using a transparent light block filter

There are three reasons i rather use an LCD: the first reason is because it is cheaper, secondly the resolution is far better, and lastly i can keep the size small and all in one box. A 22” Acer LCD resolution of 1680x 1050 is only $179 perfect size for a coffee table. The monitor combined with the cost of building materials and camera would come out to around $300 total. It would be used as my coffee table which i need anyways. I have access to a CNC machine so i can make it look good for free.

I wanted to take the monitor apart so its just the LCD. The HID would be the light source to light the LCD once the backlight and back panel are removed. Check this picture out http://images.tomshardware.com/2004/11/13/supersize_your_tv_for_/video.jpg
Its the same concept as DIY video projector just less the projection.

After that I was thinking i could use a peice of acrylic on top of the lcd.  The acrylic will be side lit by LEDs just like many other projection Multitouch displays.

Perhaps i can use Rosco between the lcd and acrylic not sure how good that would work, or like gravano said a transparent light blocker.

Think about that for a second.  You’re trying to put a light blocking filter between your IR source and the camera.

That link doesn’t work, and I still don’t know what an HID light is.  Like I said earlier, best of luck to you.  I too considered an LCD when I first got started.  But I think you need to think it through a bit more.

hrrm i can see where he’s going… ive been wondering about this method myself....

this is how i see it:

----------------------finger
----------------------compiant surface (blocks ir, maybe rosco?)
----------------------acrylic (FTIR)
----------------------lcd

\o/ |o| : light source and camera

now looking at that i see 1 major problem… the light source producing IR… but surely you could use a floresnt tube (i dont think that emits IR) or even cover the light source in a IR blocking film?

as for HID… i believe he means High-intensity discharge lamps… aka xenon - like used in some cars… pure white light and VERY bright

Is using an LCD even possible?  At least for visible light, the liquid crystals and the polarized filters would block all light passing through any pixels that are set to black.  If it is the same for infrared light, wouldn’t you have a lot of IR that just gets blocked or significantly reduced on the way through so you end up with a mottled and incomplete image?

Found this online and thought you might like to look at it for using LCD as your projector.

http://www.lumenlab.com/diy/#media

>>is using an LCD even possible?  At least for visible light, the liquid crystals and the polarized filters would block all light passing through any pixels that are set to black.  If it is the same for infrared light, wouldn’t you have a lot of IR that just gets blocked or significantly reduced on the way through so you end up with a mottled and incomplete image?
<<

it might be possible.  I’m looking at doing the same thing myself except I’m going to try DI instead of FTIR.  I took apart an LCD display last week and IR went through the black unpowered LCD panel.
what would be really nice is if I could touch the LCD panel itself and not have to have a glass surface on top of it.

I have disassembled an LCD Monitor (Eizo L360). Here is what I found out:
LCD Panel contains following layers:
----LCD
----transparent diffusing film
----reflective film with optical distortion (objects are seen with some offset to real possition on other side)
----reflective film with some polarization
----transparent diffusing film
----acryl glass painted with small white dots layouted in a grid and lights (just like FTIR)
----white non transparent film

assembled LCD Panel passes IR light from inside to outside. but it is very diffused. you can’t actualy recognize hand.
IR light from outside to inside did not passes.

LCD Panel with only LCD and acryl+light passes IR in bouth sides. You can recognize very diffused hand. LCD picture looks like a mozaik because of dots on acryl and very dark.
If you put FTIR over LCD you can actualy see blobs.
---Acryl + IR (FTIR)
---LCD
---acryl glass with dots + light.

If you put all films back (between lcd and acryl glass) - FTIR over LCD don’t work any more. But picture is not mozaik any more and looks brighter.

nesher - 02 August 2007 02:05 AM

I have disassembled an LCD Monitor (Eizo L360). Here is what I found out:
LCD Panel contains following layers:
----LCD
----transparent diffusing film
----reflective film with optical distortion (objects are seen with some offset to real possition on other side)
----reflective film with some polarization
----transparent diffusing film
----acryl glass painted with small white dots layouted in a grid and lights (just like FTIR)
----white non transparent film

assembled LCD Panel passes IR light from inside to outside. but it is very diffused. you can’t actualy recognize hand.
IR light from outside to inside did not passes.

LCD Panel with only LCD and acryl+light passes IR in bouth sides. You can recognize very diffused hand. LCD picture looks like a mozaik because of dots on acryl and very dark.
If you put FTIR over LCD you can actualy see blobs.
---Acryl + IR (FTIR)
---LCD
---acryl glass with dots + light.

If you put all films back (between lcd and acryl glass) - FTIR over LCD don’t work any more. But picture is not mozaik any more and looks brighter.

the white non transparent film at the back is I believe a reflector to reflect back any light.  also if you notice on the acrylic that there are bigger dots and more of them in the center of the acrylic.  that is because it will be harder for the light from the bulbs at edges to reach the center and the bigger white dots will reflect back more light.

my plan is to try using a bright light (hopefully one that doesn’t output any IR) and removing all the material from behind the LCD panel
including the lights on the top and bottom edges.  it would basically become a projector but without a mirror and the distance issues.
I would have to experiment with placing the various polarizer and diffuser sheets one at a time in between the lamp and the LCD panel
and see if it improves or makes it worse.

I plan on trying DI and touching directly on the LCD glass.  it should be an interesting experiment.

Ok, i’ve done the following yesterday:

Disassembled a Dell 2707 WFP LCD Screen ( Full 1080p HD resolution )
and used only the panel with the corresponding electronics (no backlight).

Here is the setup:

________________________ acryl (very thin, just for protecting the panel)
________________________ lcd panel

Patterns/Raster (for smooth/even lighting)

\o/ \o/
(ir SMD led (white SMD led
with lens with lens,
and diffusor diffusor and
pre-mounted ir cut out filter
on strips) pre-mounted on
strips)

|O|
(ir camera fire-i
with bandpass filter)

it works just great! blobs are visible very clear and sharp.

i talked with the guys from unibrain. if you use a 1.9 fisheye lens
you have only a minimum object distance of 10mm.

so the plan is to use 4 fire-i cameras with 1.9mm lenses and a
distance to the lcd panel of 160mm. doing it this way it
will be possible to reach a depth of max. 200mm of the complete
multi touch display with all needed parts (without computers
for processing the blobs etc.).

i think it is possible. and it would even be thin enough to be wall
mountable.

the only bad thing is:
approximately 2500 EUR (3425 USD) building costs.
fortunately i’ve found a sponsor!

sorry for my bad english.

Do you have some pictures for your exact setup? What did you used for the Patterns/Raster?

I will upload pictures of the exact setup sometime this week.

I used stripes of the following led’s for the raster (backlight for the lcd):

Price of one stripe: 27 EUR. I used 8 stripes.

SuperFlux-LED Stripe White 30x2000mcd 90° 500mm 12V
50cm long! Even lighting with 30xSpider LED

Color: white
Light strength:  30x2000mcd
Emitting range:  90°
Color temperature: 9000-10000K
Color room: X:0.28-0.29 Y:0.27-0.28
Voltage: 12V, 200mA

http://www.leds.de/product_info.php?info=p99_SuperFlux-LED-Leiste-wei--30x2000mcd-90--500mm-12V.html
(it is a german website)

For the infrared raster, i had to build my own stripes. But there are
stripes available for mounting custom led’s.

can you please also post some fotos or video of your setup?

Stickyb ->> Have you got some pictures?