Many people hardly understand how police laser guns operate and just how police actually aim for vehicles for speed detection. For those who haven't taken the time yet, get a quick refresher about the contrast between radar and laser.
Police laser, technically known as LIDAR means Light Detection And Ranging. Among the laser Jammer community, 'laser' is the more frequently used term, but LIDAR is also appropriate. Police laser guns might seem complicated and daunting, however with a bit basic familiarity with math along with an example or two, you can understand how it operates and the ways to, then defend against it.
Lets first examine a laser gun to ensure we are able to find out what the several parts are and the way they work.
Imagine that you are looking at the front of the police laser gun. It looks very similar to a large, boxy gun with glass lenses on the front. At the front are the laser lenses; this is the end that the office points at cars. One lens is made for emitting the light and the other is for receiving the light. At top is the viewfinder, through which the police officer will pick a target. Below, much like a regular gun, will be the trigger. Some guns will in addition incorporate a stock, which the police officer can put against his shoulder to steady the gun. There are several types of laser guns, but a majority have this gun-like setup.
Again, all laser guns have somewhat different looking characteristics, but most adhere to the same simple designs. Here is a readout in which the police officer can see distance and speed readings for his or her target. In addition there are option buttons that allow the officer to configure various options.
Now that you have a solid idea of what a police laser gun looks like, you can get a good idea of what it's like to utilize one. Overall, they are made to be really quite simple. First, with your eyes only, find a target (often a fast moving car or truck!). Next, position the viewfinder up to your eye and target the car or truck. While looking through the viewfinder, the laser gun will project a cross hairs or possibly a dot. Set the cross hairs on your target and pull the trigger. When the gun is performing normally, you'll have a speed reading in approximately a second. The system will often give off a beep. The speed reading will pop up in either the viewfinder, below, on the display, or both. The display or viewfinder can also provide the range (distance) where the speed was acquired.
So precisely how will it obtain your speed using light? Fundamentally, it measures distance! If you've seen somebody make use of a golf rangefinder on the golf course, then you've seen the identical concepts in action.
When the laser gun's trigger is pressed, the gun immediately sends out a ray of infrared light. Infrared light is outside of the visible spectrum of light, and so the light which the gun sends out is invisible, even during the nighttime. This infrared beam bounces off of its intended target, a car in this case, and is reflected back to the gun. The gun is timing just how long the beam requires to go back and, utilizing the speed of light, it establishes how far away the vehicle is.
Overall, the electronics of the police laser gun are very advanced. This technique of emitting, receiving, and timing the light will happen over a hundred times per second. That's right - per second. The pace of which this takes place is called the pulse rate, and many guns transmit light pulses at a rate of 100-140 per second. Some guns go up to even 200 per second or perhaps higher.
So what?, you say. So how exactly does discovering how distant the automobile is tell us how rapidly it is going?
At this time, the gun is computing the distance of the automobile one hundred instances every second. Because the car is moving (let's say it's moving toward the policeman for this example) towards the officer at a rate of speed, this distance gets smaller and smaller as the car barrels toward the policeman. The difference in distance is miniscule, since the measurement is occurring so frequently, however it is enough to matter. Let's return to elementary school math for a minute. Most of us learned that Distance = rate * time. If you're not great at mathematics, don't let your eyes glaze over just yet!
We utilize these types of measurement all the time - every time we say miles per hour. If you're traveling 100 miles per hour for an hour, you've gone 100 miles. Distance (100 miles) = rate (100mph) * time (1 hr). By using this basic principle, the gun measures the change in distance of the car, and from that, it has the speed!
In the event you missed it:
Gun sends out a light pulse and sees how long it takes to come back
Gun uses the time the light took to come back, and the speed of light, to compute the distance of the car from the gun
Gun performs this 100 times per second and tracks the rate of change of the distance
Gun then has Distance and Time, therefore it can solve for Rate (Speed)
And all of this occurs in under a second! Most guns only need four distance readings to be sure of a speed so, theoretically, even the gun with the slowest pulse rate of 100/second will get the speed of the car in .04 seconds!