Hi

Reading through this forum and working on 2 multitouch screens for a school project, I decided I wanted a LCD FTIR setup to use at home, for testing and photoshop etc.
Because I already have a Philips 220WS 22” monitor, and have no money for a beamer, I think I have to take the risk and open the LCD screen to see what I can do with it! Spec sheet (PDF)

I already ordered a big load of 850nm IR leds from LEDS-buy.nl (13 cents/LED), and there is some free plexiglass waiting for me at school (cut to size by a laser -> no sanding!)

I am going to use a Sony DCR-HC14E digital video recorder, with nightshot enabled it’s the perfect infrared camera! Connected with firewire I hope I get a high framerate, the first tests I did were very promising.

Oke, enough blabla. Let’s show some pictures of my (very slow) dissassembly of the LCD screen:

With only 4 screws and some gentle force I managed to remove the back of the panel.

There was this little connector on the back, but it was removable from the circuit board. I made a good start!

The front panel was easily removed, no screws!

After removing 2 screws, the front panel could be seperated from the circuit boards. There were some wires though still attached:

They could all be seperated from the screen, with simple connectors

The protective cover of the LCD driver board was easily removed, now I had to be carefull not do damage the tiny flat cables…

After removing another metal piece I saw the complete front-screen. Looks like the glass is glued on it, or something. Don’t know yet.

The backside has some white paper, with the backlight underneat it. Now it was really getting interesting…

I managed to remove the complete backlight, with no damage! Yay!

There are some layers of material between the backlight and the LCD screen. A diffused plastic, a silver-like screen, another diffused plastic, and another see-through screen.

After writing this I’m going to test if everything still works, and how good Infrared light can pass the different screens. So stay tuned for new updates!

Edwin

What kinds of resolution / framerate were you getting in your initial tests?

Great LCD disassembly pics! Looking forward to your tests of the individual screens.

Jonathan

Hi

I just tested my screen, in a complete dark room, with a halogene lamp as background (did not hook up the backlight of the LCD yet, short cables).
It worked! This means I didn’t destroy the screen!

I placed the camera underneath the screen (wobbly test) and tested to see if infrared could pass the screen. I used my remote control from the TV from this.
Funny to see whas that normal light (I don’t have a filter yet) is completely filtered out by the LCD, but infrared can pass without any troubles!

I tested some of the additional layers that were between the backlight and the screen when I opened it, but all of them diffused the infrared and made the blob fuzzy. I think they are meant for a good distribution of backlight, so I will use them in front of the backlight.

I have one question… How can I measure the framerate and maximum resolution of my firewire camera?

Later I’ll post some sketches of the box I am planning to build!

Hello

The last few days I continued working on the project. I made some cool progress, and tomorrow or next week it will be finished xD

Let me first start with a 3D drawing of my casing, I use mirror foil instead of aluminium to have reflection of the infrared.

After my dissassembly I had to test if everything still worked. You never know! And it worked!

A quick and dirty setup to test:

Screen on, no input yet, but the standard menu was visible! I used a halogene lamp to have a bright source, not the backlight because of short cables.

The backlight did still work!

That poor screen, all ripped apart:

All on a table, soon to be multitouch enabled!

A quick view of my workshop at school, with a laser cutter, 3D printer, turnbenches (don’t know the exact word) (draaibanken?)), etc.

Punch - machines. To make holes, cuts, etc. Really usefull!

It’s quite big actually!

My touchscreen! With no wires attached yet…

The LED’s are on a piece of MDF, with mirror foil under it. A hole is cut in to it to let the connectors through. All the IR light is reflected into the acryl, i hope

Soldering again, took a long time but was worth the effort. They all worked! I use two 9 Volts PSU’s, both 3 A. In total there are 66 LED’s, 33 per adaptor.

I’m a big fan of a nice soldering job. No messy wires this time! (see my previous posts on 2 multitouch screens in showcase)

And all is made of simple MDF wood, cut to size by the beloved workplace employees. All free!

And with the LCD in place, the acryl can take position. It fits perfectly! I left the plastic on the LCD, it was glued on so I decided to use it for support instead of damaging it while trying to take it apart.

And now I am sanding my ass off, to make the sides as clear as possible. I used 220,300 and 600 sanding paper. Tomorrow I’ll use a polishing machine, and hope it will be oke. Then I’m going to finish the rest of my box.

So stay tuned

sinnsyk, very nice work so far, very clean and well done , just love it! Keep it up, it’s inspiring!
Ah and you are so lucky to have such tools at your disposal
keep us posted!

Thanks!

After I sanded the sides, I tested the FTIR effect using my camera (in daylight without filter). My fingers were visible, and I don’t know if it gets even better in darker conditions with a filter, but I do hope so. I have 6 mm acryl, so I hope I won’t be needing a compliant surface..

Anyway, I continued on my box. I ordered some wood from our woodshop, cut to size. My box is going to be something like: H 38 x W 54 x D 40 cm..

I got myself some mirror-foil, so that all the light inside the box is being reflected to the screen. I am going to dress up the walls with it.

Gluing the box around the screen-frame:

Glueing the mirror foil inside the box, looks very crappy in the photo’s but in real live it reflects very good..

And with the bottom plate also glued on, it looks very shiny!

The finished box, with the top also in place. I’m going to make it removable, so that if something is wrong with the screen or the LED’s they are still accessable.

And it looks like this when the cover is opened. This is going to be some soort of door, to keep everything easy accessable when something does not work etc.

Next wednesday I’m going to install all the electronics and wire it up, and then test if it all works!

Awsome job so far! I have a question tho. What are the mirrors for? Just reflecting the IR light around in the box?
I don’t know if this applies to your camera/ setup but when you turn nightvision on doesn’t a IR light on the camera turn on. I would think that would mess up something, unless your going for a sort of DI FTIR hybrid.
anyways I hope your build turns out well

The mirrors are for the light from the backlight, not for infrared. I want a good brightness at every part of the LCD.
And there is an infrared lamp in the camera, but luckily I can turn it off in the menu..

@sinnsynk

this is too cool!

am following post to the very end…

looks like a great piece of work sinnsyk, the LCD has been hacked pretty neatly! would like to do a similar setup sometime, goodluck with the remaining work

I finally had some time to continue on my project, and I installed all the electronics.

I ordered 2 x 9 V power supply’s from conrad, and I thought that they were small and not so heavy. But they turned out to be huge! They can handle 3 Ampere each! I only need like 1 Ampere....
So now I have 2 supply’s, and I only use one that is also too big to fit inside the case.....

First I made PCB holders from MDF, to be easily glued on once in place.

You can see them a bit blurry on this picture.

It looks messy but it was the only way to place them so that the cables would fit.... and it’s inside the box anyway..

Testing it with no computer, the standard (no input selected) message DID appear. So it still works!

Another look at the circuitboards.

With my camera I did some tests, and the blobs were very bright!

Also, with our other prototype (the FTIR-Beamer-screen), the blobs were even better! The next image is a raw camera image :D

I played around with the demos etc, but the tracking of gestures is not so good. If you place your fingers, you don’t have to press really hard, but if you move, it’s hard to keep the FTIR effect going. So I’ll guess it’s time to find some compliant surface.
Next thing is to finish the box, make a sort of door, and find some brighter lights instead of my backlight. And hopefully, install my PS3 Eye (I didn’t recieve it yet)!

in a few days ill post some more!

Your project is an inspiration!

I’m *SO* glad that you specifically tested to see what impact the black/blocked state of the LCD would have on the infrared. I was terribly concerned that would be an issue with one type of LCD or another. Even with your report, I’m still a bit concerned. Are you (or anyone else here) aware of any specific make of LCD that would actually block infrared light as well as visible light when the display approaches or is black?

I am using a *very* similar camera for my setup and while I’m going to be doing either DSI or Rear-DI ... I’m very excited by your results! Keep the information coming about the progress of your table!

Cheers, A

I don’t know really about the IR transmitting specifications of LCD’s. It does not seem to matter whether it’s on or off, but perhaps thats for my LCD.

Perhaps this is of any use:

Picture/Display
•LCD panel type: 1680 x 1050 pixels, Anti-glare polariser, RGB vertical stripe
•Panel Size: 22"/55.9 cm
•Effective viewing area: 474 x 296 mm
•Pixel pitch: 0.282 x 0.282 mm
•Brightness: 300 cd/m²
•Contrast ratio (typical): 1000:1
•Display colours: 16.7 M
•Viewing angle: 160º (H)/160º (V), @ C/R > 10
•Response time (typical): 5 ms
•White Chromaticity, 6500K: x = 0.313/y = 0.329
•White Chromaticity, 9300K: x = 0.283/y = 0.297
•Maximum Resolution: 1680 x 1050 @ 60 Hz
•Optimum Resolution: 1680 x 1050 @ 60 Hz
•Video Dot Rate: 205 MHz
•Horizontal Scanning Frequency: 30 - 93 kHz
•Vertical Scanning Frequency: 56 - 76 Hz
•Aspect ratio: 16:10
•sRGB

Well… after doing a bit more research… I think I now know why my concern was founded, but didn’t materialize into a problem. The LCD relies upon light being blocked 100%. It does this with a pair of polarizing filters rotated 90 degrees from one another. A light beam hits the first polarizer, passes into the LCD matrix and, in the case where no twisting occurs within the LCD matrix, hits the second polarizing filter and is blocked because its polarized angle is blocked by the second filter. With the LCD matrix between the two polarizers, it can “twist” the light and cause it to pass at a different polarized angle. Because of this, no light that is passed through one polarizer should get through the second polarizer without first being “twisted” by the LCD matrix. In the case of “black” colors, no light should be allowed by the LCD matrix by not performing any twisting of the light.

This *should* mean that NO light gets through in the black areas of an LCD… including non-visible light (such as that in the infrared spectrum).

This was the cause of my concern.

Why is everything okay? Because LCD manufacturers are cheap and not concerned about the fringes of the visible spectrum. By concentrating the polarizing filters on the middle of the visible spectrum, they only let in minuscule amounts of visible light and they don’t care about the rest. This allows for less expensive non-glass Polaroid film to be used for polarization. The disadvantage of the Polaroid film is that it doesn’t polarize as much of the light or as much of the spectrum. To do that, would require a absorptive polarizer using elongated silver nanoparticles in very thin glass plates. SOOOO… unless you’re dealing with an LCD that has these types of glass plates in them… you should be just fine. (There are other sets of techniques based on beam splitting that can be applied, but it would be very space intensive and therefore not very well applied in LCD applications.)

I hope that puts other folks minds at ease if anybody else was concerned about this problem.

Cheers, AndrewG

Thank you AndrewG for your explanation. I really had some doubts about trying to use a LCD. Probably with my luck I would get an LCD that would block the Infrared light. Now with your explanation, I’m thinking in using an old LCD to make a new multitouch table.

Sinnsyk you’re making a Great Job, a very nice presentation. It’s so good that I’m thinking in making a similar one to test the LCD solution. I hope you’ll show us your finished work soon, we are all very excited to see it complete.

The best of the best from, Nelson Batista

hi sinnsyk
your pics are great helpfull thank you
i want to know what kind of comliant surface would you apply for increasing ftir effect in dragging?
it should be transparent so you ca see lcd panel right?