# Thread: How does LASER work?

1. ## How does LASER work?

I was going about 65ish on a 55 speed limit on this bridge. Right when I got off the bridge my Escort X50 goes off to LASER with a loud noise that just scared me. I slammed on my brakes a little because I got so nervous, and brought the speed down to 50.

I was scared that the cop had me. How does this laser work? And was there anyway I could have been caught? There were many cars on that bridge besides me, I might have got lucky.

Are there anyways I can escape the laser?

2. Escape = Laser Jammer

How it works:

http://auto.howstuffworks.com/question396.htm

3. By having cars around you is the only way you can get lucky in getting an early warning with laser. If the LEO is aiming at you, the only thing your detector is doing is giving you an early warning of a ticket.

Like bauzer71487 said, laser jammers are your only defense against laser........aka, lidar.

4. ## Re: How does LASER work?

Originally Posted by sikhkd
How does this laser work?
Laser guns do not use the Doppler principle like radar guns do. Instead, they use "time difference of arrival". The laser gun sends out a pulse, and calculates the "time of flight" for the pulse to be reflected back to the laser gun. Since the speed of light is a known value, the distance between the laser gun and it's target can be calculated by the time of flight. The laser gun takes multiple distance measurements, and by comparing the different distance measurements over time, it can determine the speed of the target.

Originally Posted by sikhkd
Are there anyways I can escape the laser?
The best way to avoid a laser ticket is to get a Jammer. Sometimes they don't JAM it completely past the Officer but it will give you early warning which is enough time to slow down before he acquires your speed.

5. I'd be more than willing to bet that the officer had a reading on your original speed, but didn't have the motivation/desire to go after you.

Laser, as other said, basically works by timing how long it takes pulses of light to travel to and from your car, and does this many many times very quickly, and a built in microprocessor determines/validates speed or distance information about you.

As far as deterring laser, you can do so with passive devices such as special laser license plate covers, or VEIL coatings over reflective surfaces of your car. Both will dramatically decrease the officer's effective shooting range, so you either

(1) have a chance to react before he can get a reading
(2) if the cop is strategically waiting to shoot you at close-range, you have a chance to visually see the cop and slow down.

A laser jammer, though more expensive, provides better protection against laser. It is not legal in a few areas, so check first.

Neither is a failproof defense. generally speaking from what I've seen in testing, both have some sort of "punch-through" distance -- that is, at X feet to the officer, the defense does no good. Active defenses have shorter punch-throughs than passive ones (usually).

6. Originally Posted by jdong
As far as deterring laser, you can do so with passive devices such as special laser license plate covers, or VEIL coatings over reflective surfaces of your car. Both will dramatically decrease the officer's effective shooting range, so you either

(1) have a chance to react before he can get a reading
(2) if the cop is strategically waiting to shoot you at close-range, you have a chance to visually see the cop and slow down.
While I agree with the rest of the post, the quoted text can be misleading.

There are a lot of variables when it comes to passive laser countermeasures. There is very little quantitative data on passive laser countermeasures, so the quoted text is true only when certain stars line up.

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