# Thread: Veil and laser shield lab tests

1. ## Veil and laser shield lab tests

I got the above from Roy recently and spurred on by Boxter's example
I thought I would take some measurements.

Different from his test, I am measuring the transmission through the material in question, not the reflection. Since I think we're trying to prevent laser light from reaching the plate (or headlight), and prevent reflected light off the plate from reaching the lidar unit, I think this is the right measure.

First I measured the laser shield by itself. This allowed ~23% of the light at 905 nm through. (If light had to pass through twice (to the plate and then back) this would be ~.23^2=5%. Since intensity falls off as the square of distance, I think this means that if this were the only reflective surface, you would have to be at 23% of the distance for the LEO to get the same return signal as your distance without protection.) Since there has been some question of which way out to mount the laser shield I tired it both ways and (not surprisingly IMO) it was the same. I also tried it at several angles around 10-15 degrees to simulate off-angle targetting and this had no effect on the transmission.

Then I tried the laser shield with one fairly heavy, I think, coat of Veil on the smooth side. This had a transmission of ~18%, or 3% after two passes. So I'm thinking it's probably not worth Veiling the laser shield.

All measurements had ~10% measurement error from trial to trial depending on exact placement of the laser shield.

The ultimate test would be if boxster could put a piece of a retroreflective license plate in his type of spec and try these tests on reflection.

2. Very interesting! I always like to see lab tests like this. Even with the 10% uncertainty you're still looking at decent reduction in the return since the light has to pass through twice. .33^2 = 10.9%.

To take this the next step, I just did some rough calculations to see how that correlates to targeting range. Honestly, things come out kind of ugly. Let's assume that maximum targeting range is 4000' on just a retroreflective license plate (some of these devices can work out to a mile.) Assuming that the beam width is 18" at 500ft (beam area = 3.141*9^2 = 254 square inches), you're looking at a beam width of 144" at 4000ft (beam area = 3.141*72^2 = 16280 square inches). The area of that bigger circle is 16280/254 = 64 times the size of 500ft circle. So the light reaching the plate from the gun is 64 times as intense at 500ft as at 4000ft. Yikes!

To calculate the net return R to the gun, I'll use R = P4000*I*S where P4000 is the beam power at 4000ft (I'll call it 1), I is the amplification factor due to distance (1 at 4000ft, 64 at 500ft), and S is percentage of light that passes through the shield. I'm going to assume that, due to the retroreflective material, all light that reaches the plate goes straight back to the gun. (This is true in theory.)

At 4000ft with no shield, R = 1 * 1 * 1 = 1, which is the baseline.

At 500ft with a shield (conservative number), R = 1 * 64 * 0.109 = 7. This means that the return at 500 feet with the shield could actually be 7 times as intense as a non-shielded plate at a max targeting distance of 4000ft! So the plate cover should have no effect at all!

Using the real laboratory number, R = 1 * 64 * 0.05 = 3.2, which is still a larger return. So, in theory, the laser shield shouldn't work at 500'.

Using the number for the veiled plate cover, R = 1* 64*.03 = 1.92. Still a larger return.

The more important part:
I also did a calculation to see how far the plate cover should work. This basically means finding the point at which the cover's return reduction overrides the increased intensity of the beam at the shorter distance. Based on my assumptions, the break-even point using the lab numbers (0.05% transmission) is 889ft.

For a Veiled plate cover, the break-even point is 695 feet.

My conclusions:
I don't know about you guys, but I think this passes the sanity test. My numbers are pretty much what the SML tests have shown in the past. And the truth is that if an officer is shooting you starting at 1000ft at highway speed you really don't have much protection. At 75mph (110ft/s) you're talking about between 1 and 3 seconds of reaction time if your detector responds instantaneously.

3. Brick,

May I suggest you read this?

http://www.laserveil.com/veil-testimonials/

Veil Guy 8)

4. No doubt, Veil is good stuff. I'll probably put a coat on the back of my Laser Shield after doing these calculations because having the best countermeasures is certainly better than having none. However, I just don't buy the concept of jamming a laser gun all the way down to zero. It makes no numerical sense even if I still have conservatisms built into my calculation, or ancientintegra has conservatisms built into his measurements.

Don't get me wrong, I'm not knocking these products. I'm just trying to be realistic in my expectations. (And my job bores me, which is why I have time to do this stuff!)

5. brick,

We concur. That's why we don't make such claims and we generally speak in terms of reaction time and not so much distance.

It's been established that a radar detector - alone - will not likely provide one with enough warning to slow safely down whilst being laser targeted.

The purpose of Veil is to provide the critical reaction time - in many cases - to safely slow down (if need be) whilst avoiding detection by the laser operator.

Will it work in all targeting situations? Not likely. Nor, do we claim so.

However we will take the occasional JTG when it happens!

Just between the two of us - we have something new in the works that should help Veil's perfomance even further. :wink:

Veil Guy 8)

6. Ooh, upgrades! I won't tell a soul. :wink:

7. Originally Posted by brick
Ooh, upgrades! I won't tell a soul. :wink:
Me either!!

8. so should i keep the coat of veil on my lasershield.... or just take it off? plate covers arent legal in jersey and with the veil on the shield my plate just seems a little dirty but a p r i c k LEO might write me up for it...what do you guys think?

9. Originally Posted by The Veil Guy
brick,

Just between the two of us - we have something new in the works that should help Veil's perfomance even further. :wink:

Veil Guy 8)
Cool! Could you give us a very general time as to when you think this will be ready? Are we looking at 3months... or more like 1 year away?

10. Bob you are a tease!

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