nbk2000
September 17th, 2002, 12:42 PM
Lately, I've been playing around with a laser pointer while goofing off outside. I'm in the middle of a freeway, with a car lot a couple hundred yards away.
Well, I've been practicing aiming my laser at the reflectors of the cars so I can see them "blink".
This gave me the idea of using a laser to detect vehicles at ranges farther than you could see them at night with the naked eye.
The basic idea is that practically all vehicles have reflectors on all sides, and license plates are usually retroflective as well.
(A UCLA researcher is already using the laser reflectance idea for automated driving. <a href="http://ansl.ee.ucla.edu/ancg/iris/iris.html" target="_blank">http://ansl.ee.ucla.edu/ancg/iris/iris.html</a> )
You'd use as bright a laser as possible, pass it through a line-generating optic, then use this to "scan" the area of interest while looking for the telltale flash of laser dazzle off of a car reflector.
By combining an IR laser with an NVD, you'd be able to detect vehicles at great range while remaining invisible yourself.
I've (in the past) used a $200 NVD to pick up the visible red laser pointer reflection off of cars a kilometer or more down the road.
I've been able to pick up cars parked on the other side of bushes where I couldn't see them by the reflection of the laser light of their reflectors, without the use of an NVD.
I tried explaining the concept to a piggie that often parks in front of my store. He (not surprisingly) couldn't grasp it in his feeble mind and said "That's what a spotlight is for!" and proceeds to light up the carlot with his.
"Great. Not only can you see them, but they can see you as well...for a 180 degree angle at more than a mile, while you can only see them within a 20 degree angle for a few hundred yards." :rolleyes:
With the laser, the incident light at long distance is too weak for a person at the target site to see the light unless they're looking directly into it. Anymore than a couple of degrees off axis and forget it, you're invisible. And that's only if you use visible light.
Anyways, the use that comes to mind (to my mind anyways <img border="0" title="" alt="[Wink]" src="wink.gif" /> ) is scanning for vehicles waiting in ambush down the road from you.
For instance, after the store robbery, while being driving back from ID'ing the punks van, I saw how they had their "perimeter" set up to catch the guys. They had a marked unit parked about a mile up the road with its lights on, but no one in it.
Another half mile up the road from that was another pigmobile with its lights out sitting in the dark, with a cop in it.
This would mean that they set the lit car as a decoy so that the perps would see it empty, go past it thinking they escaped, then be spotted by the cop sitting up the road in the dark (where they couldn't see him).
A cheapie NVD with an IR laser would be able to spot a parked vehicle at a kilometer, while the target wouldn't even know they'd been spotted.
Without the laser reflection, a blacked out car at a kilometer on a dark road would be invisible.
Another thought that comes to mind is all the reflective crap that cops wear, like their badges, gunbelts, etc.
In deep bush, you'd likely not be able to see them directly, but laser glint off of any reflective surface would stand out quite readily.
Well, I've been practicing aiming my laser at the reflectors of the cars so I can see them "blink".
This gave me the idea of using a laser to detect vehicles at ranges farther than you could see them at night with the naked eye.
The basic idea is that practically all vehicles have reflectors on all sides, and license plates are usually retroflective as well.
(A UCLA researcher is already using the laser reflectance idea for automated driving. <a href="http://ansl.ee.ucla.edu/ancg/iris/iris.html" target="_blank">http://ansl.ee.ucla.edu/ancg/iris/iris.html</a> )
You'd use as bright a laser as possible, pass it through a line-generating optic, then use this to "scan" the area of interest while looking for the telltale flash of laser dazzle off of a car reflector.
By combining an IR laser with an NVD, you'd be able to detect vehicles at great range while remaining invisible yourself.
I've (in the past) used a $200 NVD to pick up the visible red laser pointer reflection off of cars a kilometer or more down the road.
I've been able to pick up cars parked on the other side of bushes where I couldn't see them by the reflection of the laser light of their reflectors, without the use of an NVD.
I tried explaining the concept to a piggie that often parks in front of my store. He (not surprisingly) couldn't grasp it in his feeble mind and said "That's what a spotlight is for!" and proceeds to light up the carlot with his.
"Great. Not only can you see them, but they can see you as well...for a 180 degree angle at more than a mile, while you can only see them within a 20 degree angle for a few hundred yards." :rolleyes:
With the laser, the incident light at long distance is too weak for a person at the target site to see the light unless they're looking directly into it. Anymore than a couple of degrees off axis and forget it, you're invisible. And that's only if you use visible light.
Anyways, the use that comes to mind (to my mind anyways <img border="0" title="" alt="[Wink]" src="wink.gif" /> ) is scanning for vehicles waiting in ambush down the road from you.
For instance, after the store robbery, while being driving back from ID'ing the punks van, I saw how they had their "perimeter" set up to catch the guys. They had a marked unit parked about a mile up the road with its lights on, but no one in it.
Another half mile up the road from that was another pigmobile with its lights out sitting in the dark, with a cop in it.
This would mean that they set the lit car as a decoy so that the perps would see it empty, go past it thinking they escaped, then be spotted by the cop sitting up the road in the dark (where they couldn't see him).
A cheapie NVD with an IR laser would be able to spot a parked vehicle at a kilometer, while the target wouldn't even know they'd been spotted.
Without the laser reflection, a blacked out car at a kilometer on a dark road would be invisible.
Another thought that comes to mind is all the reflective crap that cops wear, like their badges, gunbelts, etc.
In deep bush, you'd likely not be able to see them directly, but laser glint off of any reflective surface would stand out quite readily.