Focus at 1000-3000ft? What is needed?

Define problem. Will it blind people? Can it cause eye damage? Is it legal? Can it leave one open to lawsuits? Does it violate OSHA regs?
Is it worth the risk when there are lots of other way to provide security?

Not trying to be an @#$ here but when one doesn't know the difference between LEDs & Lasers are they going to have any idea on safe laser use?
I find it hard to ignore issues that are clearly not safe concerning IR. Apparently it can make me kinda harsh.
I think it was

fastline said:

I don't think we will run into too much issue.

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To me that feels too much like saying we can just ignore any laws & regs since the people who might be affected won't know.

I don't want to get into a legal debate on the issue.

I think we have a few issues solved and/or found. I was going to run some calcs for watt density or energy/area to see how much will be needed at the sensor. Is there a calc floating around here by chance?

<5mw is legal, won't blind people, won't cause eye damage. I wouldn't worry about a law suit either, because anybody who crosses the laser would be trespassing and they wouldn't even know there was a laser.

These are for outdoor, overnight hour operation, 1mile from any homes. I don't see 5-10mw being a large concern. 50BMG? different story.

I should add that we have people around that are more experienced than I with this. I just don;t want to waste company time on it. Thanks a bunch for the help. I think we did find a USA builder that seems like they can nearly build anything we need so I see little use to waste time building one if we can buy for 10 bucks.

Well, I think they advertised .8mrad on a 5 or 10mw in 780 wl. We can probably make that divergence work to use more than one laser but I will have to call about the special build. Probably will order an off the shelf piece for now for testing and go from there.

benmwv said:

<5mw is legal, won't blind people, won't cause eye damage. I wouldn't worry about a law suit either, because anybody who crosses the laser would be trespassing and they wouldn't even know there was a laser.

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5mW at visible wavelengths is generally regarded as safe due to the blink reflex being fast enough to prevent damage at that level. This doesn't apply to IR. Even 780 is too dim to our vision.
<5mW IR will indeed cause damage. Will it blind you? nope. Is damage acceptable as long as you can still kinda see? nope.

5mW is legal to buy. 5mW in an outdoor installation less then 2.5 meter above ground isn't permitted even at visible wavelengths let alone IR. Night use increases the hazard since your pupils are dilated.
In the USA it is illegal to harm trespassers. Even if they break in, still illegal. Only in self defense or in a couple states against active theft. Yes, burglars can sue & they have won after being injured from "security devices". Are you likely to be sued? Not with a little luck. Are you likely to be caught if you point 200mW 980nm into random stranger's eyes? Not with a little luck. Can you be jailed & sued into bankruptcy if your luck sucks?

"and they wouldn't even know there was a laser." Back to 'we can just ignore any laws & regs since the people who might be affected won't know'. Love that one.

Also fastline didn't say <5mW, just whatever works at 3000ft with an unknown sensor. He certainly has not expressed any concern for safety.

"and they wouldn't even know there was a laser." Back to 'we can just ignore any laws & regs since the people who might be affected won't know'. Love that one.

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Well, it's true. And it's a relevent part of the decision making process too.

People ignore laws all the time with little harm done. Speeding, rolling stop signs, lack of turn signals, no seatbelts, etc. In fact, How many people on this forum do you think have *never* shined a IIIb or IV into the sky or outside of their homes... because, as we all know, it's not OK to shine powerful lasers around publicly without the permits. Despite this I'd wager a solid 95%+ of us use our lasers outside the letter of the law.

Heck, I shoot guns in my back yard occasionally and live in a small house in the city.
It's not allowed AT ALL but the chances of getting cought are extremely slim.

Risk is a parametric factor... chance of getting caught coupled with severity of consequence. If the chances of getting caught are nearly nonexistent, then the activity is not very risky despite serious consequences. The opposite holds true as well; if an action is extremely apprehendable but terribly inconsequential the risk for such activity is still low.

Personally, other than opening yourself up to civil suit, I find the prospect of a IIIa IR security laser very inconsequential in addition to having little chance of being discovered.

LazyBeam said:

In fact, How many people on this forum do you think have *never* shined a IIIb or IV into the sky or outside of their homes... because, as we all know, it's not OK to shine powerful lasers around publicly without the permits.

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Incorrect. Do some fact checking

steve001 said:

Incorrect. Do some fact checking

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Well as I see it neither of you can make a statement like that. You have no possibility to either verify or reject each others statements. On a personal thought I would think that a lot in fact do play around with their laser pointing it at the sky at some point in time to see how far it goes Just take a look at the various beamshots on this forum. A big part of those are taken outside and I am almost certain no permit was ever apllied for or granted for these situations.

LaserAdct said:

Well as I see it neither of you can make a statement like that. You have no possibility to either verify or reject each others statements.

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I can verify that. http://laserpointerforums.com/f44/arrests-64774-2.html
At this time there is no federal law requiring a variance or preventing anyone from shining a laser into the sky for personal amusement.

Laser perimeter sensors using low power IR, exist and are legal. Just CLASS IIIA laser products, no big deal. For a one off on your own property, no one cares if you make it eyesafe. 5 mW of CW IR is not going to do eye damage even if you focus it with eye surgery equipment, which uses as much as 3-5 mW for aiming beams.

I'm sure the Iranians have had beam break for the last 20 years, purchased at Radio Shack which used to sell them. So forget the "Are you USAians?" comments, which are well intended but kinda whacky. The Navy Seals and many cops have neat ways of getting around them, without the fake mirrors used in Hollywood movies, anyways.

Since no one here so far is a optics professional, and has told you what you really need to, I'm going to say this.

Look, you need to collimate a 780 nm laser, which is barely visible on paper at point blank, and 1/3rd so people have genetics that prevent you from seeing it at all. Keep the power at about 5 mW, and then run it into a 10X beam expander. Adding power above a certain threshold just is a waste of money, it is better to use better optics. A Riflescope, backwards, is a poor quality 3X upcollimator.

Modulate the laser, use a 1 to 10 khz modulation with at least 80% modulation depth. This aids in detection. A simple solar cell is too slow for long distance detection, a human does not block the beam long enough for the capacitance of the cell to discharge in most cases. So you need to use a fast detector, and the modulation helps you ignore background, which is considerable. The sky glows at near IR at night, and the bad guys know that too, nothing new there. (Oxygen Skyglow)
How laser systems deal with rain and snow will not be discussed in this post or by pm.

You need about a 10:1 Newtonian collimator.
Go to surplushed.com and get a 3 cm focal length lens and a 20 cm focal length lens. The 20 is going to need to be at least a inch in diameter, if not more. Use the TV camera mentioned below to help you arrange the lenses.

Meredith Instruments sells what you need, diode wise, and will have the initial collimator to insert the diode into.

Or just get a 1 mW hene from Ebay or Meredith. The .1 mRad beam does not need much upcollimation.

Next go over to electrooptical.net, Phil Hobbs web site.
He has a PDF on using bootstrapped photodiodes as sensitive detectors.
You need that, to get enough sensitivity.

The output of the Hobbs circuit goes into a bandpass filter tuned to your modulation frequency, a clipping circuit, and a LM555 missing pulse detector.
This forms a basic lock in amplifier topology, think of it as a tuned radio system for the laser light.

A two to four inch lens with a F1 focal characteristic, ie the focal length is about the same as the lens diameter collects the light.

Get a IR pass visible block filter from Meredith. This makes sure your detector just sees the IR.

You'll need a black and white CCD camera to see the laser for aiming. 25$ from Supercircuits.com. Some camcorders in night mode might just work just fine. Color cameras have filters that often block IR.

Now for the tricky part. Air currents from convective cooling of the soil are going to mess with your beam over very long distances.

So you need to up your possible breakage beams to more then one. You need to fold the beam back and forth a few times, or use a couple of beams spaced vertically. You then need to look for co-incidence, ie more then one beam being broken at one time.

Pro systems get rid of this by using multiple short hops.

Enjoy the false alarms from deer.

You'll need to use 3 point Kinematic mounts to adjust the laser, details at Thorlabs.com. Buy one MM2 or KM2 mirror so you can learn how to make them, they sell the needed 80 pitch screws and taps for the adjustments.

1 watt modulated Leds have been detected to 10 miles or more.

The upcollimated laser record for hobbyists is upwards of 100 Km between mountains, using photomultipliers and less then 50 mW of laser power.

I really suggest cameras with software for this, modern PC based security is pretty good.

Everything I mentioned is off the shelf and googlable. All the circuits are found on OP-AMP and LM555 data sheets.

No, I do not build custom gear for non-corporate or non-educational entities, unless it is for special needs persons, helping charitable causes, or science fair projects. I've gotten burned more then once.

Good luck with your project, but cameras with IR leds for illumination and Passive IR motion sensors work better and are cheaper. Around 21$ a sensor unit. They run off 12 volts and you daisy chain them.

A good camera system will set you back a few hundred, plus recycling a old pc.

The good guys have ways of defeating them, I'm sure. Bad guys don't.

Low cost thermal security cameras exist too, and watching the deer and the bunnies is fun.

I'd go into more details, but my kind of systems are hard to defeat, and I really dont like giving that away.

Laser beam break schematics have been published in old electronics magazines for twenty years. This is not new.

I used thermal motion for my own back yard for years, and it was easy to get at Home Depot. Alarm supply companies sell cheap modules with relay outputs. Phone wire is cheap. Beeper goes off in the bedroom, and 150 watts of floodlights went on. About two to three falses per night, mostly fast moving dogs, and coyotes, even though we're pretty much city folk with a big yard. Soon the beeper got hooked to a switch.

Again, enjoy the false hits.

The system did deter entry, with the lights. Although our problem was a peeping tom and the local kids throwing eggs. Adding a border collie to the system took care of him. Silent, smart, and they nip just right....

Dang eggs can really mess up white al siding when they freeze. Vinyl took care of that.

Mom, God Bless her, with a baseball bat, learned to listen to the sensor and scare the crap out of the kids when she caught up with them.
Hint kiddos, do not stay behind the bushes when the neighbors have a son who does research grade electronics. He can vector mom to an initial point.

Any good alarm technician could have told you this. My point is, skip the laser. Its a pain in the neck outdoors. Its great along perimeter fencing, because people along a fence will break the beam, again, and again. For the amount of time spent developing a beam break system, you can buy something newer and proven.

Real pro systems use something else entirely.

Steve

steve001 said:

I can verify that. http://laserpointerforums.com/f44/arrests-64774-2.html
At this time there is no federal law requiring a variance or preventing anyone from shining a laser into the sky for personal amusement.

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There was just a slight change that could, at least in theory, make it a federal offense to point a laser into the flight path of any aircraft, not just directly at an aircraft. That's a lot of leeway, of course who knows how or if there would be any enforcement if all you're doing is pointing at a flight path and not the aircraft itself.

LSRFAQ said:

Obama Signs Bill:

from the laser light show mailing list:

Yesterday, U.S. President Barack Obama signed a bill which includes a provision making it a federal crime to aim a laser pointer at an aircraft, or at the flight path of an aircraft in U.S. airspace. The language in H.R. 658's Section 311 will become Title 18, Chapter 2, Section 39A of the United States Code. A complete text of the law is below.


U.S.C. TITLE 18, CHAPTER 2

Sec. 39A. Aiming a laser pointer at an aircraft

(a) OFFENSE -- Whoever knowingly aims the beam of a laser pointer at an aircraft in the special aircraft jurisdiction of the United States, or at the flight path of such an aircraft, shall be fined under this title or imprisoned not more than 5 years, or both.

(b) LASER POINTER DEFINED -- As used in this section, the term `laser pointer' means any device designed or used to amplify electromagnetic radiation by stimulated emission that emits a beam designed to be used by the operator as a pointer or highlighter to indicate, mark, or identify a specific position, place, item, or object.

(c) EXCEPTIONS -- This section does not prohibit aiming a beam of a laser pointer at an aircraft, or the flight path of such an aircraft, by--
(1) an authorized individual in the conduct of research and development or flight test operations conducted by an aircraft manufacturer, the Federal Aviation Administration, or any other person authorized by the Federal Aviation Administration to conduct such research and development or flight test operations;
(2) members or elements of the Department of Defense or Department of Homeland Security acting in an official capacity for the purpose of research, development, operations, testing or training; or
(3) by an individual using a laser emergency signaling device to send an emergency distress signal.

(d) The Attorney General, in consultation with the Secretary of Transportation, may provide by regulation, after public notice and comment, such additional exceptions to this section, as may be necessary and appropriate. The Attorney General shall provide written notification of any proposed regulations under this section to the Committees on the Judiciary of the House and Senate, the Committee on Transportation and Infrastructure in the House, and the Committee on Commerce, Science and Transportation in the Senate not less than 90 days before such regulations become final.

----msg ends----

Steve

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ElektroFreak said:

There was just a slight change that could, at least in theory, make it a federal offense to point a laser into the flight path of any aircraft, not just directly at an aircraft. That's a lot of leeway, of course who knows how or if there would be any enforcement if all you're doing is pointing at a flight path and not the aircraft itself.

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I would agree you have a valid interpretation if not for the word knowingly. Now I don't see the leeway like you do here's why.
It makes that clear right in the first section what constitutes an offense. The key word is knowingly. Inadvertently hitting an aircraft would not be mistaken as knowingly targeting, because it would be a brief flash and not happen after the person using the laser has realized what they did. It's very obvious when someone is intentionally pointing a laser at an aircraft or into the flight path of an aircraft we've both seen vids showing this very thing happening.

OFFENSE -- Whoever knowingly aims the beam of a laser pointer at an aircraft in the special aircraft jurisdiction of the United States, or at the flight path of such an aircraft, shall be fined under this title or imprisoned not more than 5 years, or both.

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There are flight paths all over this country practically everywhere you would choose to point. That would amount to a lot of offenses made and be rather time wasting too prosecute.

True that would be a key term.. and it can be hard to prove one's intent.