Robin 993DX

Hi group,

I was recently zapped by a police laser for doing 72 at a 45 mph zone. The stupid thing was that the 45 mph zone was at a express way toll both express lane where I have a prepaid cruise card so I didn't need slow down to pay toll. Of course that was the perfect spot for the police to write people up for speeding. This is my first speeding ticket in ten years! I think the fine is going to end up somewhere in the $300 range.

Since then I've already purchased a V1 with a remote display. And hopefully that will give me some advance warning in the future.

I have also been doing some research on the police lidar (Laser gun) subject recently, and found that there are very few companies out there that offers a laser diffuser solution. The most effective one from radartest.com being the Lidatek brand which uses Gallium laser to diffuse the police laser beam.

All of the current laser diffuser products carrys a hefty price tag, in my case I would want to have one master unit and three additional slave units basically two for the front, and two for the rear.

Since my research I have found some interesting data, I was curious if it would be possible to build our own laser diffuser. If there is any electronic expert out there that think this is possible, please give us your feed back on this subject.

Here are the data I have collected so far:

Police lidar is 904 nanometers, 5 nanosecond pulses of 25 Watt instantaneous power delivered into a 4 milliradian cone angle at 1 KHz repetition rate.

The lidar beam width at 250 meters is about 1 meter^2. The license plate (Colorado) has about .001 meter^2 of retroreflective paint. - 30 dB loss. They are illuminating the retroreflective paint with 25 milliWatts

The return beam (from the retroreflective paint) is also about 1 meter^2 and the receiving aperture is about .001 meter^2 - 30 dB loss.

The return (Colorado) is thus 25 microWatts instantaneous power. The effective measurement bandwidth is 30 GHz. Other states have stronger returns, with Georgia 14 times as strong.

Basically the two vital component of a laser diffuser would have to include:

(1). Somesort of fast photodiode which is rigged to received only the 904nm light spectrum range light and hooked up to some sort of a amplifier to generate a signal to activate the Gallium laser burst when it detect a IR light in the 904 nm range.

(2). Have (more than one) equally powerful Gallium laser diode pointed at different direction in the front and the rear of the car firing randomly generated pulses between 10 and 1000nS and vary their width randomly.

TIA

Kevin Reilly

All my college liberal arts education did was allow me to read the above post, but without comprehending any of it! <img src="graemlins/c.gif" border="0" alt="[ouch]" /> Hope you get your answer Robin!

tom_993

Let’s do some math: One $300 ticket every 10 years is $30 a year, and you’re spending how much on a V1 and a multi-angle diffuser? This is why I don’t have a V1. Are you sure it's worth the expense?

Robin 993DX

Tom,

Although the price of the ticket is only going to be around $300, but personally to me the pissed off factor was worth a lot more than that.

So the money spent ont he V1 is definitely worth it, and if by any luck if I could successfully create a working laser diffuser device I would feel even happier to know that I could cause a $5000 police laser gun to be useless.

For that it is worth it.

I don't know, maybe it would be cheaper for me to seek out a shrink to help with my anger management issue.

<img src="graemlins/c.gif" border="0" alt="[ouch]" />

Ran

[quote]Originally posted by Kevin Reilly:
<strong>All my college liberal arts education did was allow me to read the above post, but without comprehending any of it! <img src="graemlins/c.gif" border="0" alt="[ouch]" /> Hope you get your answer Robin!</strong><hr></blockquote>

What do you expect? It is usually Robin who answers others' questions. Surely when he, as owner of p-car.com, has a question, it has got to stump most of us. Not only was I unable to comprehend, but I also could not type that post with all those funny signs between the words metre and 2.

Robin, can't help much but here is a thought - since you have survived 10 yrs without "assistance", how about just writing this incident off to be a one-off. I suspect that you have the "best practices" well mastered. Just a thought.

Robin 993DX

You guys are giving me too much credit, all the data in my post were gathered from research others have done on this subject.

I am just as lost, but I guess I sure know how to pretent.... LOL!

tom_993

Robin, I fully understand the emotional side of it.

Silver Bullet, last time I got a radar ticket was in 1977. I’ve decided against getting a V1 for that reason.

Martin S.

I have posed Robin's question on an anti-Lidar device to a semi-retired PhD physicist buddy of mine, with a specialization in millimeter radar. He also is a Porsche owner and does not like to receive tickets, especially when speed enforcement is generally capricious and arbitrary, most of the time. I will hear back from him shortly and will forward the info to Robin.

I see Tom's point on the expense...but I am with Robin on the anger issue, and being able to neutralize Lidar. For every measure there is a counter measure...that is how it goes in an adversarial relationship.

Tickets are generally a revenue issue...are they are trying to keep us safe from ourselves? I wonder, do you???

tom_993

[quote]Originally posted by Silver Bullet:
<strong>Knock on wood Tom. </strong><hr></blockquote>

Totally!

Robin 993DX

[quote]Originally posted by Martin:
<strong>Tickets are generally a revenue issue...are they are trying to keep us safe from ourselves? I wonder, do you??? </strong><hr></blockquote>


Well, I can definitely answer that question.

Ever since that speeding ticket I have pretty much been driving just 5% above speed limit. I specially make sure my speed when passing through the same toll both again and try to keep my speed below 50 mph (Limit is 45 mph), and I have actually endangered myself and other motorist on several occassions because they almost ran me over....

Robin 993DX

BTW, additional information about a laser diffuser.

The responsibilities of regulating a laser light falls under the job of the FDA, since it is not a radio frequency it is not a violation of the FCC rule to shoot a laser beam out of your car. Of course only if the laser beam falls under certain class level.... In other words if you want to have a high power laser gun mounted on your car like "Michael Knight" you would still need the FDA's approval.

But with that said, I believe it is unlawful in any State to have any device installed on your car that may interfere with Police work.

And of course anyone with a laser diffuser installed would not be advertising that they have a laser diffuser installed on their car and that it would need to follow some basic stealth installation rules.

"Bad cop, no donut!"

Buck

Hi Robin, sorry to hear about your run-in with a laser sharp shooter. I used to run through the 400 cruise lane at increasing speeds to see how fast it would read my card (usually late at night). I quit when it still worked at 110. I guess I was lucky they hadn't found out what a good hunting spot it was. Kind of like hunting in a baited field.

I have a V1 and driving 2-3000 miles a month I wouldn't leave home without it. But, while it's rated good for lidar it still leaves you pretty exposed. I've had two incidents in ATL on 285 where they shot and stopped the car beside me and I never got a beep out of the V1. The beam is so focused there's hardly any stray energy to detect off axis.

I've heard one of the most effective things you can do to hide from lidar is to run with your high beams on. Supposedly, it makes it more difficult for the laser to lock on.

I may be in ATL next week. If I make I'll give you call and see if you want to go to Andretti's. We'll invite Hank if he promises to carry a couple of sand bags. He spanked me pretty good the last time we went.

Bill Z

I originally hesitated to reply, as the complex nature of the information in Robin's original post seemed to beg for a complex answer that I am unable to provide. However, to somewhat pass the buck and refer you elsewhere, a laser is just light, and shining a light, of the right wavelength "in the eyes" of the laser gun can make it unable to pick up your speed. I got this information from a "Car and Driver" test from some years ago, where the most effective countermeasure was a high powered driving light covered by a red filter, with the high beams on, on a black car. I can look up the issue and fax you a copy if you like. Bill Z

Robin 993DX

Bill,

Thank you for your input. The headlight could possibily take some risk out of the front, what about the rear?

Here are some additional information from one of the laser jamming sources I found regarding CW headlight jamming, and it confirms to what you posted.

CW Jamming sources.
Headlights aimed into .5 by .2 radian distribute their power over 0.1 steradians, at 250 meters range, this illuminates 6000 square meters or 10^(-6) of the police receiving aperture. 200 Watt lights put 200 microWatts into the lidar gun. Presumably the lidar gun has a narrow band filter passing about 10 nanometer of the spectrum, reducing this CW jammer by a factor of about 40, meaning that the light is now 5 microWatts. The detector is AC coupled so we calculate the shot noise due to this background ShotNoise = SQRT[RecievedPower * PhotonEnergy * MeasurementBandwidth] Sqrt[5. Micro Watt PlanckConstant SpeedOfLight/(900 Nano Meter)*30 Giga Hertz] = 0.200 microWatt equivalent optical power. This is small compared to the 25 microWatts return from a license plate. The Car and Driver article indicates that this jamming technique works, contrary to this calculation, and to Craig Peterson's article

Bill Z

Robin, what you write makes sense, and why high beam works better. Maybe putting the infrared filter over the high output driving light puts the most energy into the most effective wavelength, thus optimum effectiveness. Extrapolating, Keep the red lenses on the rear fog lights, but pump up the photon output. Bill Z