I am trying this as well. I have allredy dismounted and lcd panel and using it to test.

I have tried two ways of doing the backlight: its own backlight with a whole in the middle for the camera. Wont work. Even if you put it at some distance to try to get the light to difuminate the efect of the spot you can see it.

A led backlight: My leds are just 14.000mcd 14º wide so they need difusor and still you can see the spot of the center of the led.  they are separated about 4.5 cm from each other allowing for my camera to show there. But as I said the spot still there.

The solution might be to use the leds that stickyb suggested before, the ones that evenly espread the light… but I dont want to know how much they will cost.

For valentine: I dont know if the HID LAMP would work because I am not sure how even it will give the light and you probably can see more light in the center than in the size. From what I have read in the lumenlab forums, the bigger the display the worst the effect gets. And there they talk about 15” lcd maximum. Imagine the effect in a 22” screen. In the other side if it emits IR its not that bad cause you can use it to do the Rear Ilumination method with that IR light. RI is said to be better than FTIR. The idea is the same, it just changes where the light comes from.

Going to look at the price of those leds…

Hugo

Ok. So as spected those leds were expensive. Not as much as I though but expensive. The good thing is that they say they dont have a high spot in the center so they can be used. I checked and for my 22” lcd I would need like arround of 10 or 15 of those strips, wich is about 270-405 euros… a bit too much. I could almots get a projector with that. http://www.leds.de/product_info.php?info=p99_SuperFlux-LED-strip-white-30x2000mcd-90---12V.html

But they sell the leds alone also and they are way cheaper. Check here: http://www.leds.de/product_info.php?info=p1_Superbright-SuperFlux-LED-white-2000mcd-90--3-1V.html . They have a 90º angle and good power. If I buy 375 and place them every 2 cm it only costs 131 euros, wich is acceptable. Only problem is, you have to solder them. and they have 4 legs each… so thats about 1400 soldering?!?!? Maybe with less leds you can do. They have 2000mcd 90º.

Obviously its way better to pay 131 euros and get 375 leds, than paying 270 euros an only getting 300, but only soldering 20 legs instead of 1400 is tempting… hehehehehe Does someone know if some sort of pvc for leds can be buyed to make this more easy?

Stickyb if you are arround can you tell us the amount of this leds needed to give good light?

Hugo

Do you need something like http://www.lumenlab.com/forums/index.php?showtopic=21493&hl=LEDs

cerupcat - 17 August 2007 04:45 PM

Do you need something like http://www.lumenlab.com/forums/index.php?showtopic=21493&hl=LEDs

Thats too much light for an lcd. With that you would see the image of your lcd on the oposite wall. Thats why it is used on a projector. Also, they still put some difusor sheet betwen the light and the lcd, because the leds dont give even light. But with multitouch you cant have the difusor in the middle, so thats why I am looking for a led that gives even light, without the hotspot in the center.

I tried to put the difusor in the middle with a whole for the camera, but it can be seen in the lcd even if you put it at some distance (30cm). The light has to be extreamly even along all the lcd or its easily noticeable and gives a very ugly and not acceptable effect.

Hugo

this is kind of hypothetical and not exactly commercially viable right now but just because i can’t get it out of my head and it’s similar to what you’re doing i thought i’d mention it anyway, doesn’t make much of a difference since you’re half way through. if you wait for a little while longer (couple of months which is probably too long) you’ll probably be able to get your hands on an oled display (no backlight so no problem but no idea what kind of ir it would produce). not sure how to incorporate it into a diffused illumination setup but with an oled display that’s a couple of mm thick hypothetically that used as the projection surface on top of the compliant surface in an ftir setup would be the idea (multitouch display while avoiding a projector) you’re trying to get at, right?

jbolton - 19 August 2007 04:05 PM

this is kind of hypothetical and not exactly commercially viable right now but just because i can’t get it out of my head and it’s similar to what you’re doing i thought i’d mention it anyway, doesn’t make much of a difference since you’re half way through. if you wait for a little while longer (couple of months which is probably too long) you’ll probably be able to get your hands on an oled display (no backlight so no problem but no idea what kind of ir it would produce). not sure how to incorporate it into a diffused illumination setup but with an oled display that’s a couple of mm thick hypothetically that used as the projection surface on top of the compliant surface in an ftir setup would be the idea (multitouch display while avoiding a projector) you’re trying to get at, right?

Hi

I am open to any ideas, more in this moment that I am stuck with this problem. I have read in the wikipedia information about OLED. For the ones like me that didnt know what OLED was is a technology that allow the pixels to emit light so you dont need a backlight. Its having some problems in form of short life (but this seems to be solved now) and problems with pattents, so its very expensive to develop.

The question here is: would an OLED panel let IR through as does a LCD panel? If it does then is perfect. Also theres the isue that theres no extended comercially available solutions and at the beggining is probably going to be an expensive technology. Why did you mention to wait two months? What is going to happen in the OLED world in two months?

Hugo

Ok. So trying to iluminate evenly the lcd while having a little whole where the camera could see through didnt work cause the lcd is too fucking sensitive and you can see a shadow where the camera is, I tryed to make the camera see through the difuser and fresnel lens that the lcd originally had for an even ilumination. No luck.

I am uploading too pictures. In both of them my finger is on top of the lcd but you just can see the spots of the leds that rebounds onto the fresnel. Theres like a broken circle. Thats fine, thats one of the wholes I did on one of my last tests.

Ive run out of ideas and giving up. Probably going to build one multitouch with projector. So any last idea welcome.

Hugo

Hi

Before going out to dinner I did a quick test yesterday. I though I might be getting too much light from the ir leds and the difusors and fresnel were rejecting a big part of it back to the camera, and blinding it from seeing my finger. So I took out the ilumination acrilic, the disusor and the fresnel, and just left the lcd and tryied. I could see still a lot of rebounds, but basically only the hotspot of the leds. And if I moved my finger out of the hotspot I could see it. Not very bright, but it was there. So as I had allredy an ftir surface ready from the beginings of my test with multitouch I went and did the test today with ftir through the lcd, so all the IR light was coming from above and there was no rebound blinding the camera. So I set up everything today and it worked. When you put the difusors and the fresnel lens the signal is not too good, but I hope the blob can be detected. Also keep in mind that for this test I use an 50x32 cm ftir acrilic and I have only iluminated one of the short sides with ir leds for testing. Probably if I put leds in the other short side or even in the larger sides I can get a better signal.

Here are the pictures:

1)FTIR through LCD, without anything under the lcd (no acrilic, difusor or fresnel):

2)FTIR through LCD, with only the acrilic with difuminating spots under the lcd (no difusors, no fresnel):

3)FTIR through LCD with everything that the lcd originally had under (acrilic, difusors and fresnel):

Hi,

How are you illuminating the LCD panel?

and

What size is the LCD Panel / the acrylic and how many LED’s are you using?

Andy - 22 August 2007 07:29 AM

Hi,

How are you illuminating the LCD panel?

and

What size is the LCD Panel / the acrylic and how many LED’s are you using?

I am iluminating the lcd panel the way it was iluminated orinally: two little fluorescent on each side of the difusor acrilic (the one under the lcd). Fluorescent dont do IR so it doesnt interfiere.

The lcd panel is 22” widescreen, and I am using 6 of the osram leds from the wiki (the ones with 40º), placed in little wholes made in the short side of the acrilic that I made (the one on top of the lcd).

Hugo

hugolp - 22 August 2007 07:42 AM

Andy - 22 August 2007 07:29 AM

Hi,

How are you illuminating the LCD panel?

and

What size is the LCD Panel / the acrylic and how many LED’s are you using?

I am iluminating the lcd panel the way it was iluminated orinally: two little fluorescent on each side of the difusor acrilic (the one under the lcd). Fluorescent dont do IR so it doesnt interfiere.

The lcd panel is 22” widescreen, and I am using 6 of the osram leds from the wiki (the ones with 40º), placed in little wholes made in the short side of the acrilic that I made (the one on top of the lcd).

Hugo

Could you post some pictures of your setup? I’m starting to build my own screen shortly. Today i started to disassemble the 15” screen I got for free. The upper backlight lamp is broken so i have to think another way to lighten it up…

Kamelisko - 22 August 2007 02:23 PM

hugolp - 22 August 2007 07:42 AM

Andy - 22 August 2007 07:29 AM

Hi,

How are you illuminating the LCD panel?

and

What size is the LCD Panel / the acrylic and how many LED’s are you using?

I am iluminating the lcd panel the way it was iluminated orinally: two little fluorescent on each side of the difusor acrilic (the one under the lcd). Fluorescent dont do IR so it doesnt interfiere.

The lcd panel is 22” widescreen, and I am using 6 of the osram leds from the wiki (the ones with 40º), placed in little wholes made in the short side of the acrilic that I made (the one on top of the lcd).

Hugo

Could you post some pictures of your setup? I’m starting to build my own screen shortly. Today i started to disassemble the 15” screen I got for free. The upper backlight lamp is broken so i have to think another way to lighten it up...

So you want to do a 15” multitouch lcd or you want to use the 15” lcd to do a projector for the multitouch?

hugolp - 22 August 2007 04:20 PM

Kamelisko - 22 August 2007 02:23 PM

hugolp - 22 August 2007 07:42 AM

Andy - 22 August 2007 07:29 AM

Hi,

How are you illuminating the LCD panel?

and

What size is the LCD Panel / the acrylic and how many LED’s are you using?

I am iluminating the lcd panel the way it was iluminated orinally: two little fluorescent on each side of the difusor acrilic (the one under the lcd). Fluorescent dont do IR so it doesnt interfiere.

The lcd panel is 22” widescreen, and I am using 6 of the osram leds from the wiki (the ones with 40º), placed in little wholes made in the short side of the acrilic that I made (the one on top of the lcd).

Hugo

Could you post some pictures of your setup? I’m starting to build my own screen shortly. Today i started to disassemble the 15” screen I got for free. The upper backlight lamp is broken so i have to think another way to lighten it up...

So you want to do a 15” multitouch lcd or you want to use the 15” lcd to do a projector for the multitouch?

Oh this is going to be experiment only. So I’m doing 15” screen for now. Maybe later I’ll get funds to purchase 30” panel (2500x1600). But first I must be sure how to build one so that’s why this experiment.

Do you have blog or something? Mine is in http://kamelisko.pp.fi/multitouch

I’m running one at the moment - http://hmmd.blogspot.com/

Looking good so far, Andy! I’m looking forward to see DI tests! Does anybody know if the big HD screens are illuminated on the same manner?