Wanting to test home built lidar jammer

[STiMULi]

A space heater is useless against a lidar.
Don't mix up "near infrared" (IR-A ; 700-1400nm) and "long infrared" (IR-C ; 3000-10000000nm). A photodiode (SI-pin diode) has 0 sensitivity in the IR-C spectrum.
You might be able to overwhelm a lidar with a non-pulsed IR source, but you will need a lot more power then 4 watt. You will probably need a very expensive, very dangerous and very power hungry cw ir laser. The receiver end of a lidar is designed to separate background noise (sunlight, xenon headlights etc.) from its short reflected ir pulses, and it does a very good job at it.

But the IR we care about is in the 904-905 nm area

[Solion]

A space heater is useless against a lidar.
Don't mix up "near infrared" (IR-A ; 700-1400nm) and "long infrared" (IR-C ; 3000-10000000nm). A photodiode (SI-pin diode) has 0 sensitivity in the IR-C spectrum.
You might be able to overwhelm a lidar with a non-pulsed IR source, but you will need a lot more power then 4 watt. You will probably need a very expensive, very dangerous and very power hungry cw ir laser. The receiver end of a lidar is designed to separate background noise (sunlight, xenon headlights etc.) from its short reflected ir pulses, and it does a very good job at it.

But the IR we care about is in the 904-905 nm area

X2 , the IR comming from a space heater is from about 780 to 980 nm how do I know this? I have a couple of high brightness 950's I was playing with at 100mw/sr and they were very very dim in comparison to the 890's on the same IR camera. there is a limit to the sensitivity of the ccd in the little camera.

However I still hold to my claim that 4w as your minimum, and here are the numbers.

IR lasers in a lidargun have to comply with saftey standards as set by the US government. This compliance requires that all lasers fired from Lidar guns are "eye safe" or in terms set out by Class 1, Class 1M and Class 2 (however I am not sure if any Lidar guns now are class 2 or above. Professor?)

In short, Lidar output (even if they claim to have 50WATT modules) is very small. because the "on " times of that emitter are very very short. so what once was a mighty 50 watt that could burn flesh, melt steel is now about 50mw. and to be honest probly a little less than that. keep in mind I can buy a 300mw IR laser diode from ebay that I can light matches and cigarettes with (for a power comparison)

So lets take a look at why 4 watts could jam a lidar gun. as I said in a previous post we can ramp up the power quite abit on our side of things because we are not throwing our coherent focused beams of energy. So we are eye safe in that arena. But when I say 4 watts will jam, IS with the caveat of 4 watts of IR in the correct NM range to blind the detector in the gun.

When most people think of 4 watts, they think of the little 4 watt bulb used in a night light. "how could that JAM a gun ?" Well it cant, neither can your headlights because the IR slice of the spectrum of light being thrown out is so small. You may or may not have played with Prisims when you were in science class. but the basics of light breaks down to a rainbow of frequencys that make up white light , a 100watt bulb is only going to put out .0018w of the IR frequency needed to jam a lidar gun. But 4w of that same frequency would require a lightbulb the size of a van to produce it (in white light)

With me so far?

Back to the lidar gun. at 50 mw .. the gun has to be able to see its reflected pulses to calculate the change in distance over time to calculate speed. and this is where a little voodoo sets in. And another caveat, reflectivity.. Oh this is a tough one to quantify as every car is different, every paint is different , every reflector is different. How much power of the pulse is reflected back is in direct relation to the distance it can nail you at. And here is the kicker. the beams divergence over distance is pretty big., at 2000 feet it will cover your whole car and part of the car next to you.

So lets take a moment and ask. Under Ideal conditions, if you mounted a mirror to the front of your car and shot it at lets say 1000 feet. how much energy would you get back to the apeture of the gun.. well if you said 50mw, wrong .. 10 mw , wrong ..2 mw still wrong ... less? I hate guessstimation of maths, without knowing some specifics on a lidar gun , apeture size , divergence ect I will throw out a number. somewhere on the order of .01mw,

Why so low? Well remember our old friend divergence, the laser pulse comming from the gun at 2000 feet is going to be about 6 feet in dia, we will say 3 feet at 1000, even if you had a mirror, the reflected pulse at 1000 feet has to make that same return of a 1000 feet back to you. the beam continues to spread into a 6 foot cone. If you had a 6 foot lens on the front of the lidar gun, I suppose you could focus allot of the energy back into the gun. , That would be fun to see
but not practical. you are only going to get a tiny tiny slice of the pie back into the Gun with the 2 inch dia objective lens. These numbers change the closer you get , as the cone shrinks. But still you will loose quite abit of power even at short distances.

So with this in mind, how can 4 watts do the trick. Well , it depends on the car and your reflectivity index. 4 watts of 900nm indeed may not work for a car with a silver paintjob or a ton of chrome on the front. Or trucks with large vertical surfaces but for cars with lower front ends and dark in color it may be enough .

Boy did this turn into a long winded MR SCIENCE . but I think peoples understanding of Light and its properties will be helpful to push forward the Hobby of home built jamming.

[jimbonzzz]

however I am not sure if any Lidar guns now are class 2 or above. Professor?

I'm not aware of any either...

[Eloi]

< So lets take a moment and ask. Under Ideal conditions, if you mounted a mirror to the front of your car and shot it at lets say 1000 feet. how much energy would you get back to the apeture of the gun.. well if you said 50mw, wrong .. 10 mw , wrong ..2 mw still wrong ... less? I hate guessstimation of maths, without knowing some specifics on a lidar gun , apeture size , divergence ect I will throw out a number. somewhere on the order of .01mw >

Great resume Solion !

When I compare the output of my Osprey versus a tv remote ,
thru a digital cam set 2 inches form the emitter lens ,
the relative brighness is like 1 to 20 ,
I guess the secret of the sensitivity of the gun is the lens.
It is like a cat"s eye in the dark .

[Solion]

<

Great resume Solion !

When I compare the output of my Osprey versus a tv remote ,
thru a digital cam set 2 inches form the emitter lens ,
the relative brighness is like 1 to 20 ,
I guess the secret of the sensitivity of the gun is the lens.
It is like a cat"s eye in the dark .

Well sensor technology is some neat stuff. but the real trick is the fact that the lidar guns sensor is set to receive a very very small fraction of IR bandwidth at huge sensitivity. and that is its Achilles heel to overpowering it. To see some really tiny returns that little sensor has got to be incredibly sensitive. Probly on the order of 40,000 times more sensitive than the human eye.

[fulcrum]

A space heater is useless against a lidar.
Don't mix up "near infrared" (IR-A ; 700-1400nm) and "long infrared" (IR-C ; 3000-10000000nm). A photodiode (SI-pin diode) has 0 sensitivity in the IR-C spectrum.
You might be able to overwhelm a lidar with a non-pulsed IR source, but you will need a lot more power then 4 watt. You will probably need a very expensive, very dangerous and very power hungry cw ir laser. The receiver end of a lidar is designed to separate background noise (sunlight, xenon headlights etc.) from its short reflected ir pulses, and it does a very good job at it.

But the IR we care about is in the 904-905 nm area

X2 , the IR comming from a space heater is from about 780 to 980 nm how do I know this? I have a couple of high brightness 950's I was playing with at 100mw/sr and they were very very dim in comparison to the 890's on the same IR camera. there is a limit to the sensitivity of the ccd in the little camera.

However I still hold to my claim that 4w as your minimum, and here are the numbers.

IR lasers in a lidargun have to comply with saftey standards as set by the US government. This compliance requires that all lasers fired from Lidar guns are "eye safe" or in terms set out by Class 1, Class 1M and Class 2 (however I am not sure if any Lidar guns now are class 2 or above. Professor?)

In short, Lidar output (even if they claim to have 50WATT modules) is very small. because the "on " times of that emitter are very very short. so what once was a mighty 50 watt that could burn flesh, melt steel is now about 50mw. and to be honest probly a little less than that. keep in mind I can buy a 300mw IR laser diode from ebay that I can light matches and cigarettes with (for a power comparison)

So lets take a look at why 4 watts could jam a lidar gun. as I said in a previous post we can ramp up the power quite abit on our side of things because we are not throwing our coherent focused beams of energy. So we are eye safe in that arena. But when I say 4 watts will jam, IS with the caveat of 4 watts of IR in the correct NM range to blind the detector in the gun.

When most people think of 4 watts, they think of the little 4 watt bulb used in a night light. "how could that JAM a gun ?" Well it cant, neither can your headlights because the IR slice of the spectrum of light being thrown out is so small. You may or may not have played with Prisims when you were in science class. but the basics of light breaks down to a rainbow of frequencys that make up white light , a 100watt bulb is only going to put out .0018w of the IR frequency needed to jam a lidar gun. But 4w of that same frequency would require a lightbulb the size of a van to produce it (in white light)

With me so far?

Back to the lidar gun. at 50 mw .. the gun has to be able to see its reflected pulses to calculate the change in distance over time to calculate speed. and this is where a little voodoo sets in. And another caveat, reflectivity.. Oh this is a tough one to quantify as every car is different, every paint is different , every reflector is different. How much power of the pulse is reflected back is in direct relation to the distance it can nail you at. And here is the kicker. the beams divergence over distance is pretty big., at 2000 feet it will cover your whole car and part of the car next to you.

So lets take a moment and ask. Under Ideal conditions, if you mounted a mirror to the front of your car and shot it at lets say 1000 feet. how much energy would you get back to the apeture of the gun.. well if you said 50mw, wrong .. 10 mw , wrong ..2 mw still wrong ... less? I hate guessstimation of maths, without knowing some specifics on a lidar gun , apeture size , divergence ect I will throw out a number. somewhere on the order of .01mw,

Why so low? Well remember our old friend divergence, the laser pulse comming from the gun at 2000 feet is going to be about 6 feet in dia, we will say 3 feet at 1000, even if you had a mirror, the reflected pulse at 1000 feet has to make that same return of a 1000 feet back to you. the beam continues to spread into a 6 foot cone. If you had a 6 foot lens on the front of the lidar gun, I suppose you could focus allot of the energy back into the gun. , That would be fun to see
but not practical. you are only going to get a tiny tiny slice of the pie back into the Gun with the 2 inch dia objective lens. These numbers change the closer you get , as the cone shrinks. But still you will loose quite abit of power even at short distances.

So with this in mind, how can 4 watts do the trick. Well , it depends on the car and your reflectivity index. 4 watts of 900nm indeed may not work for a car with a silver paintjob or a ton of chrome on the front. Or trucks with large vertical surfaces but for cars with lower front ends and dark in color it may be enough .

Boy did this turn into a long winded MR SCIENCE . but I think peoples understanding of Light and its properties will be helpful to push forward the Hobby of home built jamming.

Sorry, but you are making several mistakes.

1) Yes I believe you, when you say that the heater is brighter in your camera then the LEDs. Some (relative) very small part of the radiation is in the near-IR region, and the camera sees a pretty wide part of that spectrum. (From visible to far into the near IR) Because these heaters have such high power, the (to the camera) visible part of the total output of that heater is still brighter then the LED.

But it is totally unpractical to flood (or blind) a lasergun, because a heater is an extremely inefficient near IR source. My guess (and it is really just a guess) is that less then 1% of the heater output lies within the spectrum you need for jamming. So 99% or more of the heater output lies not within the 780-980nm as you suggest.

2) The reflected energy from a lasergun pointed at a license plate at 600ft as seen from the 2" receiver lens by that lasergun is a much more then that of a 4 watt laser mounted on a car at 600ft.

There is one exception to this rule: The laser on the car directly beams into the receiver lens of that lasergun.

And that is the problem here. Any narrow focussed laser mounted on a car will point in the wrong direction, and will simply miss the lasergun. To solve this problem, the laserbeam has to be diverging. (Maybe 20 degrees?) Now make the calculation. A 20 deg diverging laserbeam at a distance of 600ft will project a circle of IR light with a radious of around 100ft ((sin(20 deg) * 600ft)/2) The area of that circle is 31400 sq feet. The area of a 2" lens is only 0.022 sq feet. The lasergun will "see" less then 1/1000000 of the total radiated ir laser light..............

Now I have to simplify things:
- A lasergun at 600ft will project a circle with a 1ft radius.
- The area of that circle is 3.141 sq feet.
- Assume the area of a license plate is 0.25 sq feet
- Then 8% of the laser energy hits the license plate
- Assume the license plate retro-reflects 25% of that energy to the source.
- In this case the lasergun "sees" 2% of its reflected pulse. (Assume the rest of the car doesn't reflect anything)

0.02 is 20000 times more then 0.000001

The lasergun laser is 20+ watt. Do you still think that a 4watt cw laser on the car is enough?

These simple calculations show me that passive flooding of a lasergun is unpractical and dangerous because of the power you will need for it to be effective.

Back to the heater................
Now try flooding with a heater at 600ft you'll need to install a BIG heater on the car. (maybe 20000x100x20 = 40000 kWatt)

3) You're mixing up pulse power and average power. To hide a 20W pulse you need 20W cw. And even that is to low, because light (fotons) add up, and (this is over-simplified) you will end up with 20W spikes on top of a 20W noise level. Again this can be filtered away as background noise, and the gun will still "see" the pulses.


By the way: Things become a lot easier without front license plates.

[Solion]

I think I will take each argument on order and try and quantify my statements,
First what you said:

Quote :Yes I believe you, when you say that the heater is brighter in your camera then the LEDs. Some (relative) very small part of the radiation is in the near-IR region, and the camera sees a pretty wide part of that spectrum. (From visible to far into the near IR) Because these heaters have such high power, the (to the camera) visible part of the total output of that heater is still brighter then the LED.


But it is totally unpractical to flood (or blind) a lasergun, because a heater is an extremely inefficient near IR source. My guess (and it is really just a guess) is that less then 1&#37; of the heater output lies within the spectrum you need for jamming. So 99% or more of the heater output lies not within the 780-980nm as you suggest.

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My suggestion about the heater had really nothing to do with using it as a jamming source. But more to alleviate the fears that my array or any array of
high brightness LED's (not lasers) in the 900 to 905 as being a source of power will not do eye damage. Which is what quite a few people here had worries about. I was using it as a tool to show that high levels of IR come from various sources in our world and we are not walking around with canes.

For gods sake, I am not suggesting everyone stick space heaters on their grills
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Your quote:

QUOTE :2) The reflected energy from a lasergun pointed at a license plate at 600ft as seen from the 2" receiver lens by that lasergun is a much more then that of a 4 watt laser mounted on a car at 600ft.
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Me: DID I say LASER? .. if you re-read I said IR Led at 10deg. Important difference here. And I think I did mention reflectivity as being an important factor. that IMHO 4 w was your MINIMUM not that it would jam Lidar if you have a massive reflector on your car.

As for your statement of brightness., I would like to take you up on that. have you SEEN a 4w IR LED with an IR camera? today and just for you I will take another quick video of a single 4W 850nm led. I think you and everyone will be pretty shocked. Also as a scale of brightness take a look at this video link. in it he shows the various power outputs of jammer heads. but in it as well you can see the actual rectangle beam coming from the gun. and how little in comparison it puts out to the heads.

http://www.donspc.com/vidpics/IRcombo.wmv

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Your statement:

Now I have to simplify things:
- A lasergun at 600ft will project a circle with a 1ft radius.

Me: Well depends on the gun but most agree at 500ft is 18inches

- The area of that circle is 3.141 sq feet.
- Assume the area of a license plate is 0.25 sq feet

Me: with you so far

- Then 8% of the laser energy hits the license plate

Me: In a perfect world in a vacuum on a tripod, Okay I am there

- Assume the license plate retro-reflects 25% of that energy to the source.

Me: this is where you begin to loose me. because from where I am standing its going to be less than that. but okay.

- In this case the lasergun "sees" 2% of its reflected pulse. (Assume the rest of the car doesn't reflect anything)

And ..... you lost me.. okay like I mentioned before while coherent (laser) light does go farther, divergence is an issue. you are not getting the reflected energy from the 600ft/12 inch cone. you are getting the energy from a 1200 foot/24 inch one. You don't get that back for free.
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The lasergun laser is 20+ watt. Do you still think that a 4watt cw laser on the car is enough?

Again, I think this a misunderstanding of the real power output of a lidar gun. its not 20 watts, its maybe 50mw I can assure you at no time are you getting that much energy. its a class1 device for a reason. the video pretty much proves how bright the reflected energy from a lidar gun is. But give an ahour or so . let me show you 4w.

[Solion]

As promised here is a video of an 850 nm luxon star 4 watt led. I had to do this inside as the weather is for shait today. and I dont want it to rain on my lappy


[ame=http://www.youtube.com/watch?v=jCEDlq4tjGs]YouTube - REC 00015[/ame]


I think people need to understand that there is a scale where maximum saturation occurs. first is in reflectivity and second is the sensor of the gun.

the Guns sensor has an upper limit to how much current it can pass. it is not infinite
so you can saturate that sensor to a point it will not see anything but what you want it to see.

But I do have one admission I want to make here . that led in the video you just looked at .... its not 4 w ... its 2 ....

[computerpro3]

You're totally wrong about the damage of infrared light to eyes. You can very easily damage your eyes with an infrared 3W led, and the scary thing is that you won't even know it. IR is much more dangerous than normal light because our retinas do not contract when exposed to it. We also don't squint. The IR heats up the retina and causes permanent damage. The problem is that this damage manifests itself in small blind spots that our brain adapts to and tunes out. There very well may be "holes" in your vision that you aren't even aware of.

This has been documented hundreds of times by medical journals, scientists, etc.

Sorry to rain on your parade.

[Solion]

You're totally wrong about the damage of infrared light to eyes. You can very easily damage your eyes with an infrared 3W led, and the scary thing is that you won't even know it. IR is much more dangerous than normal light because our retinas do not contract when exposed to it. We also don't squint. The IR heats up the retina and causes permanent damage. The problem is that this damage manifests itself in small blind spots that our brain adapts to and tunes out. There very well may be "holes" in your vision that you aren't even aware of.

This has been documented hundreds of times by medical journals, scientists, etc.

Sorry to rain on your parade.

Okay now, first thing I would like to do is show your work. and show me how diffused IR ... NOT LASER .. Diffused IR at 3w burns peoples retenas at distances over 1 foot.

Or I am calling you a troll

I am calling you out on such a statement. because it is blndingly silly. While IR LASERS at 3 w will fry a hole in your retina 3 watts of diffused IR from an IR Led is not going to.. SIGH . Lets take a look at a few things here. by your own statement.. that 2000 watt heater throwing massive IR has blinded me.
Every security camera is blinding people. the 4w, 6w 10w IR IR flashlights
have punched holes into your retina. THE SUNLIGHT reflecting off a bit of chrome has punched holes... gawds

Show your work , Show me the scientific evidence of your claim

Show me the energy levels of those claims

Show me medical evidence of your claims

WHY? ... I will do this one more time, just for you.

People have this weird idea about energy. The problem comes mostly from a misunderstanding of Physics or they spell it Fizziks

Why is 3w of diffused Ir not going to FRY YOUR EYES. well first thing we have to understand is that stated 3watts IS NOT going into your EYES! Now you can't put your eyeball on the lens of the emitter. But try and understand that Diffused IR from a LED is projected in a cone. just like any other source of light in other wavelengths.

As this cone spreads out the total energy has to be divided by the angle of that cone. NOW you have to figure out the amount of energy you can capture with the objective lens, (we will say 10mm for the human eye)

Do you see the light now? well no you cant .. its Infrared .. but that gets into the last part of beating this dead horse ..

Wavelength....Do you understand the difference between the energy carrying ability of UV Vs IR ? .Its usually measured in eV or energy per photon.. UV B
lets say in 315 nm–280 nm has an eV of 3.94–4.43 eV IR 750nm to 900 nm has an eV of 1.65 to 1.49 ..

Do you get it? ..

Yes there are Osha standards for steel and ceramic workers to protect their eyes, but they litterally are having to deal with hundreds of thousands of watts of IR and IR into much higher frequencies. For hours and hours daily

You Do realize that on a sunny day we get over 500 watts of IR per METER.. IMm BLIND IM BLIND!

Stop the scare and show your work. This is the last time I will address this that the 4w from my LED jammer running for a max of a couple of minutes are NOT GOING TO PUNCH HOLES IN YOUR EYES Arrrrggghh!