It would be an IR LED, not laser. Here's what I've got going on.
I have already installed a magnetic door locking device, which holds the door closed while power is applied. For entering from outside I'm using an RFID reader, which I've already successfully interfaced with my PIC. For the interior I need a mechanism to let people out (they could scan their RFID tag from the inside too, but that would not fly for fire safety).
Basically I have three options.
1 is a mechanical switch of some kind. That would require replacing the existing push bar or fitting some sort of switch bar to it. That would require the most work and fooling around.
2 is a capacitive touch sensor type setup. I would have to put some metal strips on the push bar that are insulated from the bar itself, because the bar, door and building are all metal. I did some basic research and found different designs for capacitive touch sensors, but I don't know which would work best for this, nor how they would work if someone was wearing gloves or leaned against the push bar with their body. I have seen one of these "exit devices" pre-made that is touch sensitive, exactly for this application, but it was several hundred dollars.
3 is what I'm going with, which is to shoot a beam across the entire width of the door opening (double doors, around 5 feet or so total) right across where the push bars are, and pretty much as close to the bars as I can get. Now if someone tried to push on the glass to exit, they won't break the beam. But that's okay, because the bars will be labeled "Push to Exit". This will work if someone leans up against the bar too. When the beam is broken I will keep the door unlocked for a few seconds to give them time to actually start opening the door. So I suppose that a regular IR LED would work fine at that short of a distance, and maybe, hopefully, I won't even need lenses.
Dan East