# Thread: Rear laser's silver lining?

1. ## Rear laser's silver lining?

I've been thinking this over lately. When LEOs shoot laser at the rear of passing vehicles, they are reflecting tons of laser scatter off the back of the car. This means that if an LEO shoots a car in front if you, in theory you should have a better chance of detection before you're clocked.

Any thoughts on my theory?

2. are you saying hit the guy in front of you in the rear, or hit the guy in front of you in the front............... if its from the front of the guy in front of you then yes it will scatter because thats just how it is

if its in the back of the guy in front of you, youre already either past the LEO or it wont do much since reflective surfaces will do exactly that, reflect, the only reason scatter really happens out there is that the windshilds and windows, their glass acts like a prism to the laser and scatters the otherwise coherent beam of light

3. I would guess that laser scatter, from a car in front of you would be stronger than any reflection from the back of a car in front of you.

The reason for my guess is that I think the reflection is going to require some absorption from the reflective surface, more than the scatter.

Of course, Professor Jim will likely explain this to us before long.

4. I'm picturing an LEO shooting the back of a car 500-1000 feet in front of you.

If an LEO shoots the back of a car in front of you, there has to be enough laser light reflected off of that car back to the gun to get a speed reading. If that much light is reflected back then that should be enough for a detector to alert to.

Usually when they shoot from the front, all that light is reflected away from you.

5. Originally Posted by Palut
I'm picturing an LEO shooting the back of a car 500-1000 feet in front of you.

If an LEO shoots the back of a car in front of you, there has to be enough laser light reflected off of that car back to the gun to get a speed reading. If that much light is reflected back then that should be enough for a detector to alert to.

Usually when they shoot from the front, all that light is reflected away from you.

when shot in front the bit of divergence over the glass is scattered all over the place, when youre dealing with coherent light off a perfectly reflective surface, its all about angles, the angle he shoots it at, and all that other good stuff

besides, at the ranges youre talking about you'll see the LEO sitting there, and already be slowing down, or the reflected beam will have solittle energy remaining that it really wont register, and to get a good accurate reading a LEO has to shoot a target, whether rear or front, at a decent distance of id say atleast 300ft due to cosine error at close rabge, so thus he'd have to be pretty far ahead of you to really get a warning to you, but at the same time close enough for you to take the scatter, if there is any to begin with

6. The only way I can see laser being reflected would be if they shot the retroreflective plate, which would reflect light all over the place, right?

7. take a laser pointer to a license plate, itll bounce off but still create only 1 point of light elsewhere since its still coherent, or it'll reflect right back at ya, its not exactl IR, but it is still coherent light

8. Originally Posted by ELVATO
The only way I can see laser being reflected would be if they shot the retroreflective plate, which would reflect light all over the place, right?
And the tail lights too. Most of them are retroreflective too.

GTO_04

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