IR sensor matrix or alternatives?

[PapaSnuff]

This is my first post, and first time venturing into custom electronics. I am a Software Engineer however, so I feel very comfortable with the programming aspect.

I'm building a very small **broken link removed** prototype, more like a panel than a table (only 5 inches or so). Normally, you use a mirror angled at 45 degrees underneath the acrylic surface, and a camera pointed at the mirror to capture the infrared blobs from the persons fingers on the acrylic panel. I'm trying to come up with a way to remove all that bulk. I'd like the entire device to only be about 2 inches thick. I am only interested in input, and I'm not going to be displaying anything, so there's no projector to worry about either. I need multiple inputs, so a capacitance solution seems out, and I also need continuous detection across the entire surface.

Would a panel of photodiodes in a 2D matrix work? What are some other IR detection options? I need an analog signal, not just on/off, but the resolution doesn't have to be that great (e.g. 10 sensors along that 5 inches wouldn't be horrible, but more is better).

Thanks in advance.

 

[PapaSnuff]

I realize I was probably pretty confusing in my first post, so I'll try to simplify things in the hopes of a response.

What kind of setup would be required for detecting IR light so that I could track a person's fingers on a surface?

ASCII picture of problem


________________________
|_____acrylic surface______| (~|= <---IR LED shining into acrylic from side
hm:hm:hm:hm:hm:hm:hm:hm:hm:hm:hm:hm: <---???


This is for tracking finger movement on the acrylic surface. The part I'm trying to design would go where the ohm marks are. I need a thin matrix of some sort of sensor, driven by some PIC board I assume. Basically the resulting image would be grayscale, black where there is no IR light, white where the IR light is most intense (underneath the fingers).

If this is still unclear, please let me know. I'll do my best to clarify things.