908nm laser - how can I see it?

[tomekg35]

Are there any devices available to the general public that would allow for an infrared laser 908nm to be visible. I don't necessarily need to see the whole laser beam, but at least the point of reflection on a wall, maybe.

Thank you very much for any information.

 

[joeyss]

First do you have some goggles? Make sure you do when you're playing with those WLs since you can't see them. I'd try the camera on your phone if you have one. Alot of cheaper cameras should be able to pick up a bit of that WL in a dark room if the laser is focused.

 

[tomekg35]

A couple of us, figured out that the Photo Speed Camera system used in a few towns in Maryland, has a design issue and gives out speeding tickets to innocent drivers. We also figured out what the problem is, however, to have solid evidence, we need to run a few more tests. The system used, uses two 908nm lasers from a pole 32 feet high. When a vehicle drives through the first beam, it starts a clock, then when it drives through the seconds, it calculates your speed.

The laser they use are 908nm, so invisiable. We need to determine the exact points where they hit the road. Since we can't see them, it is hard.

Anyone know anyway we can see those two dots on the road which are shut from a height of 32 feet.

Thank you for any info.

 

[123splat]

Like Joey said, most digital cameras (less expensive ones) will detect I.R.ranges. You can get I.R. sensitive film at a camera shop for the 'old film type' cameras, but it is really heat sensitive, you have to watch how you handle it. I.R. sensitive (dectector) cards are available from some electrinics shops, but are kinda expensive, and would be dificult to use for your application. Know anybody that has Night Vision equipment?

 

[Trevor]

A couple of us, figured out that the Photo Speed Camera system used in a few towns in Maryland, has a design issue and gives out speeding tickets to innocent drivers.

So what's the design issue? I can think of many ways to make this work extremely precisely using the information given. I highly doubt it's flawed like you think it is.

Also, I suspect you mean 980nm.

-Trevor

 

[tomekg35]

Trevor,
the manufact. claims it's a 908 nm laser.

It's not the laser that is the problem. It's the 32 feet pole that moves, bends, and twists.
The speed is calculated based on a 24" distance between the laser points. However, because the pole moves with a wind of less than 8mph, it possible that the two points are not exactly 24" apart like they should be during measurements, and it is also possible that the laser points reflect from different parts of the vehicle thus giving from measurements.

We have already proven this to be the case, however, to have solid evidence, it would help if we could see the points of reflection on the road.

 

[Trevor]

As soon as the leading edge of a car influences the beam, the computer will recognize that. The same goes for the second beam. This can be measured to microsecond (perhaps nanosecond) precision. Has it crossed your mind that there is likely an accelerometer or some other type of positional sensor in the pole to account for sway? That would allow easy correction of sway - and those types of sensors are not expensive.

I think there is more butthurt involved here than actual science.

-Trevor

 

[tomekg35]

Trevor it's all possible but that is not the case. Anyway, we have already proven to them that there system doesn't work correctly. Cars driven at 35mph getting 55mph tickets. We have proven that a bus or heavy truck can't be driven at 75mph at that section of the road like their tickets claimed. Not possible. Their citation always have take two photos, and they also give the exact time between the photos, so with a time difference of .386 seconds between the two, and the car travels less than 10 feet, there is no way the car was going 65mph, correct? In order for a car to be driven at 65mph, it has to move almost 30 feet in that time frame.

There are hundreds of cases of innocent drivers given tickets, however, the courts assume that they tickets are valid because they use laser and have to be accurate which isn't exactly correct. The lasers can be accurate but there are other issues here that we have.

The questions still is, is there a way for me to be able to see the exact point of reflection on the road.
If

 

[tomekg35]

"As soon as the leading edge of a car influences the beam"

We have also proven that this isn't the case, from 3d models we were able to see that the laser can strike different parts of the car. Just a few inches off, will be enough to give false readings. The way their system calculates the speed, it has to hit the car exactly in the same place on both readings. Too many times this doesn't appear to be the case.

 

[Trevor]

Get an IR detector card.

Who is the manufacturer of the system? What are your credentials?

EDIT: Ahh, Optotraffic. Yes. So do you think that box has nothing in it? No intelligence to counteract environmental conditions?

-Trevor

 

[qumefox]

Just use your cellphone or any other cheap camera like others have mentioned. My iphone sees IR in those ranges just fine.

And I agree with trevor. This is likely 'more butthurt than science' since, while the whole pole might be moving, both laser sources are likely very close together.. probably in the same enclosure. So while they may be moving as the pole sways, I think you'll find that their distance relative to each other, which is what matters.. stays fixed.

You'll have to provide some pretty hard to acquire data to get tickets thrown out due to this. You'll have to have hard proof that counters the manufacturers technical specs and testing to convince a judge.. Just a 'video of the dots moving' won't be nearly enough since you have no real proof that it actually affects speed readouts.

 

[tomekg35]

Yes, you are right it's Optotraffic...

Their technical own technical documents don't mention anything about what is the box, other than lasers.

 

[tomekg35]

We're not proving that the dots are moving; this is not the point. The point is that the are making all calculations based on the 27" rule and the two lasers dots are exactly 27" apart.
Even if they are still 24" apart when the pole moves, it may however strike two different parts of the car. Even if it's off by only 6" inches, it will give false readings as much as 40%. We have already done these calculation on 3d models. We have some very smart people work no this, we have already gotten the information that we need. The last issue is to get some more exact tests done, but without knowing the exact points of reflection on the road it is impossible.

 

[Trevor]

Then I don't think it's a very safe assumption to say that there is no compensation for environmental factors.

Plus, they are likely measuring the average return time of a diffused beam. Which is quite accurate. I highly doubt these use collimated beams. I expect that was an assumption of yours.

-Trevor

 

[Ash]

Optotraffic isn't going to post the schematic for their device online for anyone to copy.
So, let's figure out what's in the box:
Lasers/sensors/Camera
Power supply
computer
memory
wires
(maybe a gyro)

 

[tomekg35]

IF their system was this accurate than why do we have hundreds of errors. Vehicles not physically able to be driven at speeds of 75mph are given tickets for such a speed. Their photos are secondary evidence of the speed traveled, but when these photos are analyzed they show a speed of 35mph, which is the speed limit. There are many accurate and correct tickets, however, there are just too many impossible tickets.

We have drives with cars chips (which records their exact speed) going past these systems at 35mph, but still getting 60mph tickets mailed to them.

It also appears that almost all of ticket analyzed for errors, the vehicle driven was either a truck, bus or some other big vehicle.