may be the end for laser guns
Discussion
apparently, (I have on good authority) there is a device about to hit the market that doesn't jam laser guns as such, but makes 'ammendments' to the speed they display. ie if you're on a 40MPH road, then 40MPH is the speed it will read, regardless of your actual speed. - no error codes.
That WILL be interesting.
That WILL be interesting.
If I'm guessing correctly, it effectively records the pulses/modulation from the gun, and sort of 'plays' them back with a different time interval, through the laser diode, back at the gun. The speed gun therefore sees it's own signal coming back so doesn't think it's jammed. By varying the playback delay, you can synthesize a different speed. The laser diode has to create a bigger signal than the number plate, which isn't easy, and the speed gun locks to the strongest signal. Will certainly stop people getting ping'd for being a bit over, but if someone blasts past at '30MPH' it'll look a bit odd. Great if you're doing 39MPH and it reads say 32MPH though don't you think?
Makes sense.
Not jamming, just sending out a wide cone-shaped phase and/or frequency-shifted signal that denotes 40mph or 30mph or whatever.
Again, if you abuse it by going 70mph in a 40mph, your going to attract attention to yourself!
In this day and age it's worth protecting yourself I think.
Saw a Plod at top of sliproad today with a LASER gun looking down onto the M62 west bound near junction 31 I think. I got onto the slip road, saw him and went 45mph onto the motorway to slow all the traffic as trucks went to lane 2
Cheeky buggers. Why not get out onto the M-way and spot some bad driving that I see every day that causes the accidents, not a few occasional speeders that probably cause 5% of motorway accidents through outright speed alone :angry
Dave
>> Edited by Mr Whippy on Wednesday 20th July 12:31
Not jamming, just sending out a wide cone-shaped phase and/or frequency-shifted signal that denotes 40mph or 30mph or whatever.
Again, if you abuse it by going 70mph in a 40mph, your going to attract attention to yourself!
In this day and age it's worth protecting yourself I think.
Saw a Plod at top of sliproad today with a LASER gun looking down onto the M62 west bound near junction 31 I think. I got onto the slip road, saw him and went 45mph onto the motorway to slow all the traffic as trucks went to lane 2
Cheeky buggers. Why not get out onto the M-way and spot some bad driving that I see every day that causes the accidents, not a few occasional speeders that probably cause 5% of motorway accidents through outright speed alone :angry
Dave
>> Edited by Mr Whippy on Wednesday 20th July 12:31
The theory is well established...the (US) military have been investigating for a while in "active" stealth, where the wavelength and incidence of an incoming beam (radar initially, but theory apparently applies to all EM spectrum) are "cancelled" by an opposing waveform beamed down the same axis.
To create a false image after this, all you need do is either:-
a) adjust the cancelling beam slightly to create the false image/reading (not as easy as it sounds); or
b) send a second beam along the same axis to create said false image/reading.
However, to do this to, say, an LTI 20-20, you would need a series of very precise sensors around the car, at least two (front and rear) pairs of (rapidly steerable) lasers which work on the correct frequency (Now THERE's a show-stopper for starters!!!) to project the false reflection out to the gun, and of course an ultra-high speed processor to manage all this before the LTI has a reading (typically 1/3 sec?!?)
Suffice to say I doubt this is genuine.
There may be other ways of changing the reading, but these depend on how the laser operates...
- if it is by "range-finding", and doing the speed/time sums, you would need to "Hold up" every pulse slightly to reduce your apparent speed...but there would need to be an increasing delay for each incoming pulse, and how you would control such a thing is beyond me.
- if it is by doppler-effect (more likely), then my physics is currently failing me, although someone more current might have a suggestion...
To create a false image after this, all you need do is either:-
a) adjust the cancelling beam slightly to create the false image/reading (not as easy as it sounds); or
b) send a second beam along the same axis to create said false image/reading.
However, to do this to, say, an LTI 20-20, you would need a series of very precise sensors around the car, at least two (front and rear) pairs of (rapidly steerable) lasers which work on the correct frequency (Now THERE's a show-stopper for starters!!!) to project the false reflection out to the gun, and of course an ultra-high speed processor to manage all this before the LTI has a reading (typically 1/3 sec?!?)
Suffice to say I doubt this is genuine.
There may be other ways of changing the reading, but these depend on how the laser operates...
- if it is by "range-finding", and doing the speed/time sums, you would need to "Hold up" every pulse slightly to reduce your apparent speed...but there would need to be an increasing delay for each incoming pulse, and how you would control such a thing is beyond me.
- if it is by doppler-effect (more likely), then my physics is currently failing me, although someone more current might have a suggestion...
are, that's the easy bit, delaying the pulses
Why sample the signal?, just send each pulse down a different passive delay line ie a piece of wire.
We are talking nanoseconds of delay here.
Not that difficult, and a laser diode will output (even when diverged with a lens) more energy than the number plate.
Although the frequency is high, the pulse frequency is extremely low. you just divet each pulse down a longer and longer delay line with gates. not complex electronics to be honest.
Why sample the signal?, just send each pulse down a different passive delay line ie a piece of wire.
We are talking nanoseconds of delay here.
Not that difficult, and a laser diode will output (even when diverged with a lens) more energy than the number plate.
Although the frequency is high, the pulse frequency is extremely low. you just divet each pulse down a longer and longer delay line with gates. not complex electronics to be honest.
bryan35 said:
apparently, (I have on good authority) there is a device about to hit the market that doesn't jam laser guns as such, but makes 'ammendments' to the speed they display. ie if you're on a 40MPH road, then 40MPH is the speed it will read, regardless of your actual speed. - no error codes.
That WILL be interesting.
Oh I like the sound of that and I hope it works. I shall start saving up for one immediately.
Best wishes all,
Dave.
anonymous said:
[redacted]
How would you prevent the sale? Laser Jammers are available, illegal drugs are available, even Guns are (obviously) available, if there's a market there will be a way to sell it and I would think there would be plenty of people lining up to buy one if it does what it claims.
All prohibition will do is put the price/demand up.
If the device is illegal to sell in the UK they will just sell it on the Internet, transaction is then carried out abroad.
Of course if it's too good they'll soon outlaw it, or the Police will start stopping people when they suspect them of perverting the course of justice/interfering with a Rozzer (ooer).
Of course if it's too good they'll soon outlaw it, or the Police will start stopping people when they suspect them of perverting the course of justice/interfering with a Rozzer (ooer).
How does the "device" know what speed to send back? GPS system so that it always knows the limit of the road that you're on? How about temporary limits?
Dubious really, and when it goes wrong and sends back a 70 mph signal when you were actually doing 49 in a 40, you'd be really in deep keck.
Still, if they can make it work reliably and in a nice undetectable manner, I'll join the queue.
Dubious really, and when it goes wrong and sends back a 70 mph signal when you were actually doing 49 in a 40, you'd be really in deep keck.
Still, if they can make it work reliably and in a nice undetectable manner, I'll join the queue.
NEENAHHH NEEHNAHHH NEEEENNNAHHHHH
Road Safety Bill currently before the Big House and about to hit the Statute Books.
Speed assessment equipment detection device is defined as a device the purpose, or one of the purposes, of which is to detect, OR INTERFERE WITH OPERATION OF, equipment used for assessing the speed of motor vehicles.
Offence to use one attracting fine 2,500 if caught on a Special Road, 1,000 on othe road plus 3 - 6 points.
Fixed penalty Sir.......
DVD
Road Safety Bill currently before the Big House and about to hit the Statute Books.
Speed assessment equipment detection device is defined as a device the purpose, or one of the purposes, of which is to detect, OR INTERFERE WITH OPERATION OF, equipment used for assessing the speed of motor vehicles.
Offence to use one attracting fine 2,500 if caught on a Special Road, 1,000 on othe road plus 3 - 6 points.
Fixed penalty Sir.......
DVD
Dwight VanDriver said:
of which is to detect,equipment used for assessing the speed of motor vehicles.
Sooo, do we close our eyes when passing a speed camera or mobile unit then, in case we detect the speed assesment equipment?
What really peeves me off is that these devices are put at KNOWN accident blackspots, yet they want us to NOT slow down at them.
Surely they could be called "accident blackspot detectors" or something?
OK, you may well be speeding and blocking the signal, which is bad, but to ban the detector of them is just plain stupid! Surely that goes against the whole point of visible speed enforcement?
Dave
bryan35 said:
are, that's the easy bit, delaying the pulses
Why sample the signal?, just send each pulse down a different passive delay line ie a piece of wire.
We are talking nanoseconds of delay here.
Not that difficult, and a laser diode will output (even when diverged with a lens) more energy than the number plate.
Although the frequency is high, the pulse frequency is extremely low. you just divet each pulse down a longer and longer delay line with gates. not complex electronics to be honest.
I'm a bit dubious, but your method does make sense.
Couple this with the fact that it is blindingly
easy to surreptitiously make all parts of the car IR absorbant and you might be on a winner! However, this will not work at all for rear facing lidar sites; it's easy to delay the pulses, but impossible to advance them
Edited to say: I didn't think that last bit through properly. The rear protection device could start with a delay, adjusted to zero over time such that it is seen to be giving a relative advance. The distance reading might be slightly out but no-one will notice that.
When will you have the prototypes ready Bryan?
>> Edited by smeggy on Wednesday 20th July 18:37
It would be quite possible to determine the PRF from the first two or three pulses and then transmit a pulse train at a slightly faster PRF, which ought to do the trick to the required level of accuracy.
OTOH it wouldn't take much effort to develop a laser gun which emits pulses at irregular intervals, which would cabbage any system like this.
OTOH it wouldn't take much effort to develop a laser gun which emits pulses at irregular intervals, which would cabbage any system like this.
Pigeon said:I reckon the amendment to my previous post now caters for this.
It would be quite possible to determine the PRF from the first two or three pulses and then transmit a pulse train at a slightly faster PRF, which ought to do the trick to the required level of accuracy.
OTOH it wouldn't take much effort to develop a laser gun which emits pulses at irregular intervals, which would cabbage any system like this.
Dwight VanDriver said:
NEENAHHH NEEHNAHHH NEEEENNNAHHHHH
Road Safety Bill currently before the Big House and about to hit the Statute Books.
It's nowhere near hitting the statue books. It ran out of time in the last parliament and has to start again from the very beginning. It was getting quite watered down last time, and now Labour has a much smaller majority. And the truth about speeding is REALLY starting to come out...
Don't expect to see the road safety bill on the statue books for at least a year, and even then we don't know what it'll finally contain.
Gassing Station | Speed, Plod & the Law | Top of Page | What's New | My Stuff