Police LiDAR Tear Down

Most police departments made a big switch from RADAR to LiDAR after consumers starting buying RADAR detectors. A lot of those LiDAR units are now out there on the surplus market. If you don’t have $500 or so to buy a LiDAR gun just to see what makes it tick, you are in luck. [Alexei Polkhanov] spent an hour tearing down a  UltraLyte LTI 20-20 LR 100 so you don’t have to.

An hour seems like a lot for a tear down video, but [Alexei] speeds up through the boring parts, and spends a lot of time talking about the optics and how the device works (with a lot of hand drawn diagrams). He also puts it back together and connects  a scope to show the electronic operation of the device.

He mentions the display and control board uses a serial interface to talk to the controller board. There is also an unpopulated header on the main board that is clearly a serial port, probably for reprogramming the onboard microcontroller. With a little reverse engineering work, this LiDAR gun ought to be highly hackable.

In addition to the display and control board, the unit contains a high voltage supply for the laser and the photodiode. Making a power supply to drive the laser that is clean enough not to disturb the sensor is one of the design drivers and it shows. The power supply is a large and complex board by comparison to the other boards in the system.

We’ve covered LiDAR for robotics before, but the UltraLyte unit is pretty serious industrial-strength unit by comparison. If you want to learn more about how a professional LiDAR unit works, or you just want to know what technology to be mad at next time you are stopped for speeding, watch [Alexi’s] video.

48 thoughts on “Police LiDAR Tear Down

        1. I’m sorry, I wasn’t trying to be a smartarse.
          In a practical sense you are constantly fighting unit upgrades, laws (now illegal in some places, with more to follow) and the fact that some LiDAR systems measure in both directions so you need to install them each end.
          Not to mention, automated systems with built in cameras (or trained cops with handheld devices) just detect when you are close, which doesn’t give you time to slow down.

          1. The current favourite units are laser parking and safety sensors. The use lasers to measure distance for parking and checking how far you are from the car in front and behind, for safety on the road. They also happen to interfere with police laser speed guns, which is a terrible shame.

      1. You can buy LIDAR detectors at any walmart.
        As for jamming it’s been done and is not too hard but in some states you could get a fine or even a misdemeanor if caught.
        Jamming really only works for automated cameras since a cop will suspect something is up if their LIDAR or RADAR gun displays an error or acts erratically under good weather conditions.

    1. There are LIDAR jammers available. But unlike radar/lidar detectors they are illegal, if police catches you jamming their speed measurement devices you’re in a big trouble.

        1. Please do your research before posting nonsense. All Lidar jammers are 100% illegal. If police catches you jamming their speed measurement devices in the Netherlands you’re in a big trouble.

          1. Please read the post before posing nonsense. Unless the Netherlands is spelled “USA” and has an FCC or FDA, I think, maybe, just maybe, he’s talking about lidar jammers in the United States…

      1. Again more bad info.

        Laser jammers are legal in almost all states. The only ones I know off top of my head that ban them are Virginia, Texas, California but I know there are a few others.

        Quit posting bad info which you have no support for and misleading people.

        Radar jammers on the other hand are illegal everywhere on a federal level.

        1. This is a multi-national website. Meaning people from all over the world are viewing at any time, so please keep that in mind. In the U.S. (aside from a few states), you are right, but in the U.K., Canada and other places, It is illegal to jam lidar just like it’s illegal to jam RF (radar). Since the FCC doesn’t have jurisdiction over IR lasers, they can’t ban jamming lidar like they do RF in the U.S.. Unless there is a federal law enacted, it is up to individual states to ban lidar jamming. Or the cop to get creative with obstruction or interference charges…. And that has happened before…

      1. Everybody speeds in my area. It’s literally dangerous to go the speed limit because there’d be such a big speed disparity, which is statistically way more dangerous than just going fast. It won’t get you in trouble if you’re with a gaggle of other cars and going at the same speed. Problem is sometimes everybody pulls into a turn lane or something and surprise, you’re now a loan speeder.

        Of course, radar detectors, lidar detectors, jammers, and so on are all illegal in my state.

        1. You say “I have to drive fast because the others do!”
          Someone other says “I have to drive fast because Blue Footed Booby does!”
          Do you notice something?

        2. I have a hard time respecting the speed limit when so many of the highway speed limits are set so ridiculously low.

          Speed limits are supposed to be set at the 85th percentile of what people typically go on the road determined by a proper engineering study. A lot of speed limits where I live, Massachusetts, are simply illegal.

          Typically during commute time people are going 75 to 80 in a 65. The only time you are at risk of a ticket going that speed is in the middle of the night when you are the only car on the road and thus an easy target. Even staties blast down the highway doing 75+ in a 65 in the left lane pushing everyone out of the way of course no one is going to give them a ticket.

          We still have two lane highways that are set to 55… fucking no one goes 55 on them.

          Of course no politician is going to work to raise the speed limit because it would mean less money for the state. Insurance companies would lobby hard against any speed limit increase anyway because they want more surcharge profit.

          The speed limits are more about profit than safety.

          1. “More about profit” delusional. It’s less about profit and more about the fact that your simple monkey brain apparently can’t keep track of a single number. You’re irresponsible.

          2. @Fennec
            If you think about it a bit (using your large, simian brain :) ) you might think of ways you could find clues whether profit is a significant motive to speed enforcement. For example, does the number of tickets written correlated in any way with funding? Do the speed limits match what protocols say actually make roads safer? Are enforcement resources allocated in line with actual danger posed by the prohibited activity?

            If speeding is wrong because it’s against the law, surely you’d agree that profit motive playing a role in law enforcement is a bad thing, even if it were producing the best possible outcome. That is, I’m sure you’d agree that the ends don’t justify the means any more than “everyone does it” justifies committing a crime.

            Sidenote: I really wish public schools had mandatory classes on ethics, including the differences between deontological and consequentialist ethical systems. Hell, even acknowledging different ethical systems, or that ethical reasoning can rise above the level of “I think this is wrong”/”no it’s not,” would make these sorts of conversations a lot easier to have.

          3. @Fennec @Lucas just because something is a law doesn’t mean it’s founded in fact or logic. I’ve made some arguments that the speed limit is set unreasonably low and that they do not follow the 85th percentile guideline and you responded with insults. I’m not arguing for an unsafe speed limit I am arguing for a realistic speed limit that reflects the speed people actually go safely every day. Keep in mind I am talking about highway speed limits here not city roads with pedestrians on it.

            For the sake of argument lets say all speed limits were reduced by 10 MPH. Would you still be calling me a simple monkey if I argued that the speed limit would be higher? Would you be ok going 10 MPH slower because someone decided that was the law?

            Well something similar to that actually happened. The reason a lot of speed limits in the US are set to 55 and 65 has nothing to do with safety. It was in response to the 1973 oil crisis.


            I would also argue that cars in 1973 were much less safe at highway speed than cars made today.

            Also if the highway speed limit was raised it would obviously mean less income for the state. That would create a budget gap which would need to be filled somehow. Now tell me what politician is going to say, “I’m going to raise the speed limit and raise your taxes in order to fund it!”. It’s too much risk and no political gain for them.

            I would rather be a monkey than a sheep.

          4. I can attest this for the most part. I live in a fairly small country(read: hick) town, and two of our four lanes are set at 45. There are numerous very narrow, very curvy rural roads with speed limits set at 55 and blind curves galore. Mind you, Schumacher would have trouble reaching that speed on these roads… ‘Safety’ is just an excuse to lower speed limits on more frequently traveled roads and collect money. I commute on both four-lanes and a couple rural roads and nearly every morning, I see at least one person stopped by police. Guess on which roads.

        3. True where I live on the freeway you better go with the flow and travel the same speed as everyone else or you’ll create a hazard.
          You also must speed to pass someone going 40mph two lane highway.
          If you spend 40 seconds performing a passing operation you risk getting into a head on collision or ending up in the ditch so the quicker you can get it done the better.

      2. @Fennec
        For that one time that you needed it…

        @Blue Footed Boob
        Driving faster than speed limit because the other cars doing so, really does not matter to the police they will ticket you just the same and often occurs by means of photo speed enforcement.
        Also, it is more likely — that if a lot of people speed in your area — that you will have more speed traps and more active radar on the road.
        Bottomline….the police will give each person a ticket and they don’t care why you were doing it.

        If you want to beat the radar/lidar/etc …. go the speed limit.

        1. “.the police will give each person a ticket”
          I don’t know where you live, but in my area police officers are usually homo sapiens, and are thus unable to be in 10 different places at the same time in order to pull over an entire group of cars in order to ticket them.

          Also, I have never gotten a speeding ticket, and I don’t intend to. I drive about the speed limit, maybe a mile or two more depending on traffic and weather/visibility. I have been told by police officers that they are instructed not to attempt to hunt down and ticket people for going 1-2 miles per hour faster than the limit because this could easily be caused by speedometer miscalibration/different tire sizes/ etc and it doesn’t represent a substantial statistical threat to other drivers nor does it necessarily imply criminal intent by the vehicle operator.

          In some locales, maybe they are more firm.

          It is always frustrating to me however when I encounter a traffic zone where everyone is going 20 mph or more over the limit in fairly heavy traffic as it does tend to make it unsafe to obey the law. I’ve never seen someone ticketed for this as it appears that police target outstanding speeders rather than the average driver.

          1. >are thus unable to be in 10 different places at the same time in order to pull over an entire group of cars in order to ticket them.

            Where I’m from, they ping you with their lidar gun, which records your number-plate too. A few weeks later you get a ticket in the mail, with photographic proof if requested.

          2. We call it tag teaming though I’m sure there’s an official name for it. Used to happen quite a bit before cameras became all the rage.

            You get two (sometimes 3 though rarely) that work in concert. One hangs out at point A and pulls your ass over. You’re instructed to drive a little further until you reach point B where cop #2 is hanging out, usually just out of sight around a bend. Cop #2 (though sometimes the cops will swap places) will proceed to write ticket while Cop #1 loops back around to point A. If there’s enough morons, he’ll usually catch a new speeder before cop #2 is finished with the first speeder. The process repeats until drivers get clued in or the cops get bored.

            I used to memorize all their favorite hiding spots as a youth and used to see them have as many as 7 or 8 vehicles lined up at once. I assume their license plate is written down or their drivers license is taken to ensure they don’t run.

            That is California where most people speed or at least push the speed limit. Different states have different driver personalities.

      1. Many of these penalties represent a regressive tax aimed at the masses to reduce the tax liability of the wealthier.

        Tax brackets stop progressing while still in the middle class.

        1. Most municipality laws have absolutely nothing to do with safety and instead exist simply as a means to get extra income.
          A good example is the red light cameras in Arizona when they stopped getting red light violations they turned them into speed cameras and of course they would go off on as little as 5mph over which is practically zero increased risk.
          Now going 50 mph in a school zone or residential street would create a safety hazard.

          1. In all fairness – Who the fuck drives 80 km/h (50 mph) in a residential area or school zone? Are you INSANE?

            The limits are 30 mph (50 kmh) in Denmark in residential zones and often 20 or 25 mph (30 or 40 kmh) in school zones. Sometimes even down to 10 mph in tight spaces.

            50 mph is road speed outside cities. I’m a pretty confident driver and I would never even attempt 50 mph inside any kind of residential area.. It might go well for quite some time, but you have zero tolerance for error when someone pops up.

  1. “Most police departments made a big switch from RADAR to LiDAR after consumers starting buying RADAR detectors.”???

    Citation needed… no pun intended.

    Not really. “They have ADDED lidar to their arsenal” would be a proper assessment.

    There are a few reasons why they haven’t replaced radar with lidar completely. One of them being that there is no such thing (so far) as “moving mode” lidar in traffic enforcement. Meaning that a patrol officer would have to remain stationary to catch speeders, and a lot of the time, that isn’t the most effective use of resources.

    So police continue using radar so they can continue to move while sampling traffic either with the radar constantly on, or toggling the RF hold switch. Hard to defeat with a radar detector if the cop is good at it and you don’t spend your money wisely on a decent radar detector.

    Lidar is good for singling out individual speeders in dense traffic, because it has a very narrow beam compared to radar. You would have a pretty decent argument in court if the cop was blasting a 20 foot wide beam of radar at 8 lanes of rush our traffic and issuing tickets at random. With lidar, you get about a 3 foot beam at range. Which makes it harder to blend in with the rest of traffic. Some of the even have a “tailgating mode” which will indicate unsafe distances between cars.

    But as far as being a “radar replacement” not happening any time soon.

    1. Oh, and I own two or three kustom pro-laser III’s and an ultra-lyte 20/20 LR. The pro lasers are built so much tougher than the ultra-lyte. It feels like a toy in comparison. and my ultra-lye has a survey mode for distance measurement. But they all three have a serial out port right on the unit, with selectable data protocols for feeding giant displays and laptops both. But I don’t see how it would be useful beyond traffic surveys. You still have to aim pretty tight with a lidar to get a reading, its more difficult to just aim it down the road and “spray and pray”, the reflectivity of cars varies wildly enough that car to car, you may have to adjust your aim a bit or the range at where you start getting a reading will vary. I think most people have this idea that lidar is just “point and click”, when really it’s more of an effort. Moving mode radar with “instant on” is the same way, you have to try it to get an appreciation for how much effort it takes. >:)

    2. Well, I take your point. They didn’t replace them. But my underlying intent was to point out that LiDAR guns have been around long enough to show up as surplus.

    1. Last time I made one, it was just an oscillator, a FET, and some IR LEDs. I don’t know what the magic frequency is, but I started with a circuit intended for CIR modulation (38kHz) and trimmed it ’til it tripped a friend’s detector.

  2. Since “jamming” is considered “illegal” in most parts of the world, and;

    (1) requires equipment mounted on your vehicle’s front and rear to be effective, plus the laser manufacturer will just keep writing new pulse code timings or maybe even scramble the timing altogether making it completely unpredictable.

    (2) No way to effectively absorb the laser, thus no way to effectively control laser reflection.

    (3) Lastly, any abnormal and/or lack of distance reading, will be perceived suspiciously by a human operator.

    THEN SOLUTION: Why not focus on finding a way to “FRY or RENDER” every activated LIDAR unit inoperable upon use on a motor vehicle, by none lethal means to the operator of course? Burn the IR receiver eye or port some how?

    This would be a two fold win! It would no only create an situation in which proof would be lacking to support allegations of traffic violations, as well as put costly units out of use, AND generate additional cost to repair or replace them. FINALLY making it too costly of a model to continue pursuing. Turn the ideology back around and redirect the financial deterrent measure to the poacher preying on defenseless drivers. Their actions in plainest terms can be defined as “CHEATING” because the odds are heavily stacked, if not completely rigged in the LIDAR operator’s favor. How can one consider this treatment “FAIR PLAY” when motorist are left with no choice but comply or pay dearly, and then still comply, or face financial exhaustion by all angles, including insurance lost.


    1. Your statement about fair play is confusing to me. “…when motorists are left with no choice but comply or pay dearly…” Isn’t the choice simply binary? Obey the traffic laws OR risk a costly penalty. Seems to me that question is something I’ve had to deal with all my adult life.

      Are you complaining that life isn’t fair?

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