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laser alarm system

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Does perfect laser mean the laser will kill the intruder? Or is it to be used to detect them?

More details if you want others to help you.
 
Yes, give us some way to distinguish a perfect laser alarm system from one which is less than perfect so we will know if we have succeeded or not. It's pretty hard to tell what done means with no measuring stick.
 
Hi,

Yes, i have tried to use those tiny cheap laser units as alarm beam
sensors, but over distances i find they 'spread' quite badly.
They are indeed far from perfect.
I was wondering about lens correction to try and reduce the spread.
But such a lens would hardly be a lens at all.

Then again, i may have misunderstood your rather sketchy post.

John :)
 
Beams of every type spread out over distance. It's what they do. A lens can focus a beam to a spot, but after that it diverges again.

Maybe that's OK, we still don't have any requirements from the original poster yet. If you shine a beam on a sensor and detect an interruption that would form the basis of an intrusion alarm. The problem is that you can see and avoid visible light. Every cheesy Holywood movie about art thieves will show you that. So what kind of radiation can be generated and detected which is not detectable with the eyes?
 
You sure about that? Last time I checked eyes are very sensitive to temperature. Can I shine an IR laser on your retina?
 
People who have a laser intruder detector outside report that the beam misses the sensor and causes a false alarm when the wind makes them move a very small amount.

There is a tall free-standing transmitting tower in my city. It has a laser at its top that shines straight down. It moves very far when it is not very windy.
 
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