to get even lighting turn the leds around facing away from the lcd then buy a reflective diffuser commonly used by photographers. It will reflect the light evenly

blitzcrege - 27 August 2007 11:53 AM

to get even lighting turn the leds around facing away from the lcd then buy a reflective diffuser commonly used by photographers. It will reflect the light evenly

Hi

This you say sounds interesting. Two things:

1- This is probably not important. The led is on the way of the light, but probably as is almost transparent hopefully it wont affect.

2-You have to put the camera. I have done some test on a even ilumination and making a 2cm diameter whole to let the optics of the camera through makes the whole thing to not work. You have to think that the lcd is fucking sensitive to not even light.

Be glad to see any test.

Hugo

sorry took so long to reply. didn’t mean specifically two months, i think i read somewhere sony is going to start releasing oled tv’s around the holidays so monitors probably wouldn’t be that much longer, still a long ways away and new technology is always expensive. would think just based on simple explanations of how it works that it wouldn’t filter ir if an lcd doesn’t but i could easily be wrong. i had just stumbled across an article on crave/cnet so just decided to mention it if you were looking to explore it as an option sometime (probably a long time) in the future.

I just disassembled a LCD-screen: http://kamelisko.pp.fi/multitouch

I tried to put copper wires inside the LCD to test how capasitive sensing would work.

It seems that you need VERY thin wires or transparent ones. LCD:s backlight system is very sensitive to objects between it and LCD panel. Check the blog:

http://kamelisko.pp.fi/multitouch

Kamelisko - 04 September 2007 03:09 AM

I tried to put copper wires inside the LCD to test how capasitive sensing would work.

It seems that you need VERY thin wires or transparent ones. LCD:s backlight system is very sensitive to objects between it and LCD panel. Check the blog:

http://kamelisko.pp.fi/multitouch

Hehehe you are discovering the same I did. Good to know someone else is working in this direction. Hope we can get to a solution.

I ordered some spider wide angle leds wich are supose to give a very even light, so when Ill get them Ill try and post results.

Hugo

I’m working right now on collecting everything to build a similar project. The plan is:

====== Acrylic+IR
----------- LCD Panel (w/out any other parts)
~~~~~~ IR transmissive white screen
|0| / |0| Lights + IR Camera

I’m still pulling together all of the parts, but I have almost everything. Still looking for a
IR transmissive white screen. I was wondering if some of you guys who have your own
setup’s could test a couple of different materials to see how well they transmit IR.

If it is not possible to find a suitable IR transmissive screen, my other thought was to use
a two way mirror, as in the following:

The LCD would stay (for the most part) completely intact (lighting etc). Additionally, there
may be no need for a compliant surface overlay. Unfortunately, this doesn’t help with the
overal size very much, but LCDs still provide higher resolution for a cheaper price than most
projectors, and since I’m wanting to build a 22” screen, a projector is kind of overkill.

Please PM me with your results. Any help would be greatly appreciated.

Have a look into using an acrylic mirror, they dont reflect IR light well, so maybe that could be a cheaper option to a 2 way mirror.

http://www.youtube.com/watch?v=6mV4ecEbV1s&mode=related&search=

Athough, he doesn’t show there being transmission, so possibly it’d just absorb the IR..

interesting cool video!

I watched your video, and although it was cool, it was of little relevance. I have revamped my design a little after doing some testing of my own with an LCD and mirror. In the original design, the “mirror side” of the two way mirror would be reflecting an image, where-as the “see-though” side would be where the IR-camera would be. The effect visible in the video of the mirror (glass/plexiglass?) reflecting very little IR shouldn’t be an issue since the mirror is only being used to reflect visible light. Unfortunately, this 45 degree mirror design would cause the viewing angle to be fairly limited. I have embedded an image of my new throught process which I believe might be more viable.

The mirror is used to reflect the light through the LCD while hiding the IR camera (etc) from view. The one problem I associate with this design is that the distance from mirror to LCD must be quite small otherwise duplicate images will occur to the user. One way to get around this is to use a clear diffracting plastic sheet to make the mirror image “fuzzy”, however this might also affect blob definition. I am in process now of trying to find a solution to the duplicate image problem, any help on this would be greatly appreciated.

Just make sure you get some test samples to try out. It’s always possible whatever coating they use for a 2way mirror could absorb IR.

About the video, I feel that it seems very relevant when combined with the suggestion. I was only suggesting it as a cheap alternative to a 2 way mirror, though, you would want to also get some scrap or sample pieces to test that out, in case as I said earlier. Acrylic mirror is very cheap. 2way mirror I imagine would be a lot dearer.

I misunderstood, you are absolutely correct. In fact, they make acrylic two-way mirrors, and that was what I was planning on purchasing.

Ahh cool. Let us know how your results go

I did a little more experiment with the wires. I took some very thin wire from regular IDE-cable. The wire itself aren’t visible but it casts nasty shadow to the screen. But I tried also to put the wire behind the backlight acryl. From there the wire is completely invisible. So if I replace the acryl with much thinner one I could get the grid to only maybe 5-8mm away from the screens surface. Maybe that distace is small enough to use the capasitive sensing? I don’t know..

I really like your idea of capasitive sensing. Any ideas on how it would work? Have there been postings on the subject in this forum? I think moving away from using webcams for IR detection would be the best end result of this technology, whether that is by using something besides IR (capasative) or by having an LED array of photodiodes. The photo-diode idea may be a bit difficult with the size of current LEDs and other photodiodes.

http://www.youtube.com/watch?v=7kzIHMpOt20