Some questions about FTIR display from a newbie
Posted: 11 May 2012 09:49 AM   [ Ignore ]
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Hi guy! I’ve been lurking around the forums for about a month or so now and this technology has really caught my attention. I believe I have a good enough understanding of most of the components to be able to attempt to build a table based on the FTIR method. I still have a few lingering questions though.

I would like to use an LCD screen for the display because I am worried about loss of quality with a projector and trying to find a good position for a projector to display the image properly. The problem I now run into is that I’ve read some people have problems with the compliant surface distorting the image. They solve this by simply taking the compliant surface and acrylic away, but then how does the camera detect blobs when you have taken away the entire FTIR portion of the table? I may have misread things but that is the general idea I am getting. I believe PeauProductions once said that you could not do FTIR with an LCD, but then I see 2 or 3 other people who have managed to do it. I think this would be the best choice of a display for me and want to make sure I know exactly how everything works before I commit to buying a screen.

If the LCD screen ends up not being an option, does anyone have any advice on finding a good projector? I would prefer it to be under $400, but if I must stretch a little I should be able to do it. I have been waiting to actually design the table until I found a suitable projector because I know a major factor on the size will be the throw distance. I am currently considering the Acer X1261P.

To help give an idea of what my final product should be like, I want a coffee table type setup. The screen will be in the middle and have some space on the sides to rest cups or other objects. To deal with any spill that might happen, I have chosen to use a 225 Neutral Density Frost Lee Filter which is supposed to be waterproof, if I remember my reading right. The screen itself may be anywhere between 26” to 36” depending on what kind of size the image turns out to be after I got the projector set up, or after I verify that the LCD route is a viable option. The main function of the table would be a sort of entertainment center. I plan to have speakers embedded into the frame and we would be able to play music through them. Using a program called TVersity I will be able to stream movies to an Xbox 360 console to play on the television that is also in the living room. The table will be used for games and the like.

If anyone has any questions or needs more information, please don’t hesitate to ask. This is a big project for a 1st timer and I’m going to need all the help I can get!

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Posted: 14 May 2012 02:01 PM   [ Ignore ]   [ # 1 ]
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It seems that if you could use lasers above the surface and the camera can see the blobs, then you could use an FTIR layer there and the camera would still be able to see the blobs.  Hopefully someone confirms this.  I know you can’t do Rear DI with an LCD, because the IR doesn’t make it through very well coming from behind the screen.

I can’t speak about a compliant surface because my setup is LLP and doesn’t need one, but my LCD came out a little less bright because I had to change the lighting anyway, so that’s a thing that can happen if you have to change your back light.

The main reason I personally still wouldn’t want a projector is because I’d feel like I need to turn it off, not leave it on, though if I wanted a large setup that may be the way to go, just to not risk damaging a large LCD.  You can end up with pros and cons that you didn’t expect about either choice, but here are some cons:

LCD:

-have to deal with the PCB attached to it by delicate ribbons
-risk of damaging when opening and working with, smudging and debris get in between layers while handling
-have to be very careful about scratching any of the layers
-have to extend the wires on the high voltage CCFL’s or make a new backlight/system
-have to find a way to secure it (if it doesn’t have one)

Projector (I have not used one so these are just my “feelings"):

-more expensive (potentially)
-bulbs have a life span
-have to deal with a mirror
-have to deal with mounting angle(s)
-have to get some kind of diffuser layer

It’s a fun project either way.  I think no matter which route you choose you will end up finding more work than you expected, just to make things perfect.

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Posted: 14 May 2012 10:21 PM   [ Ignore ]   [ # 2 ]
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Thanks for the input! I think I’m going to go with a projector setup for this one. It seems to have less risks but the trade off is more work. I may revisit the LCD option once I have more experience or knowledge/funds. The projector can be reused in any number of ways but I feel that once I take the LCD screen apart, it will become too fragile and any other purpose it could be used for would be lost. I would still like some suggestions on which projectors could suit my needs. I would like a ~32"-36" display. Does anyone know of how I would go about finding the throw distance for any specific model, given the desired screen size? Now that I’m back to using a projector the table’s size may be greatly affected by this.

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