Laser targeting showing distance of vehicle and speed in KPH.
A laser gun combined with a cam corder in Spain. Laser and Photo can be combined to photograph the speeding vehicle. They want their money for all the expensive toys they have.
Kustom Pro III Laser Gun. This is probably the most used laser gun in the USA and Canada.
Riegl Laser Gun used in Europe, manufactured in Austria
Laser Atlanta, one of the three best laser guns, but does not have a high usage around the world.
When police use laser guns to get your speed, they are essentially pointing a light beam or a long pointing stick at your car. Imagine what a flash light beam looks like at night time. The light beam spreads out very quickly, but a laser beam holds its pattern for a much longer distance. And this beam is what a laser jammer detects.
The beam of a laser gun is easily aimed at a traveling vehicle, such as yours, and scanned across the front grille area at a typical 400 to 600 feet. At those distances, the laser beam is about 12" to 22" wide, depending on manufacturer of the laser gun. Even if you had an excellent radar detector up in the windshield, it probably would not detect the laser beam down on the front grille of your vehicle, due to how narrow the beam is. And if your radar detector did alert, remember the laser beam is pointing at you only, thus your laser alert means the policemena already has your speed. Detecting laser is not helping you at all. Laser = Light Amplification by Stimulated Emission of Radiation.
The typical laser diode used in a laser is an infrared, semiconductor, GaAs laser diode. The light energy has a wavelength of 904nm (nanometers). The typical beam width is approximately 12" wide (0.3 m) at 100 m distance, or 2.5 - 3 ft wide at 1000 ft distance. The laser beam looks like a picket fence, a bright pulse of light, followed by a shawdow, then a bright pulse, another shadow, typically between 40 to 70 pulses, travelling at the speed of light down the highway.
Laser guns calculate distance by measuring the time of the infrared light pulse. Laser tools which meaasure distance will compare the incoming laser wavelength with the phase of the outgoing light. Any solid object will reflect back a certain percentage of the emitted light energy. This only needs to be a small percentage for the laser detector to pick the singnal up.
The time is measured for the laser pulse pulse to travel to the target and back. The time accuracy is extremely important, thus a crystal oscillator is used as the controlled time base. The speed of light is constant, therefore it is easy to calculate the distance the laser pulses have traveled. For increased accuracy and statistical averaging, the laser sends anywhere from 40 to 70 pulses down the highway in a laser burst. All of these pulses or the majority of these pulses need to be received in a single measurement period. Target acquisition times range from 0.3 to 0.7 seconds.
Sophisticated error trapping algorithms are in place to ensure a reliable reading. Here are the pulse frequency used by the majority of laser guns used worldwide. Stalker LZ-1 130 pps Laser Atlanta 238 pps LTI Marksman, Ultralyte, Ultralyte LR Rev 02 125pps LTI Ultralyte LR Rev 01 100 pps Kustom Prolaser III, Kustom ProLite 200 pps Kustom Prolaser II 238 pps Kustom Prolaser I 380 pps Jenoptik Laveg (European) 600 pps Jenoptik LaserPatrol (European) 100 pps Riegl (European) Let's make a quick comparison to radar signals and laser signals.
If you could color a radar beam the color of a red cloud, the radar beam expands outward very quickly, such that at 300 feet a Ka radar beam may be 300 feet wide and 75 feet tall. One can see that if there are 4 vehicles on the road, a radar beam can identify, if a vehicle is speeding, but 99.5% of radar guns used today can not identify which vehicle is speeding. Contrasting a laser beam to a radar signal, the laser beam is just 12" to 15" wide at distances of 400 to 600 feet. A Laser Gun is a pointing device.
You can aim the laser beam at the leading vehicle or the 3rd vehicle back, by aiming at the headlight. When aiming the laser beam at a vehicle, it is the same as aiming a pistol, thus the person using the laser gun peers through a sight and physically aims the laser beam down the highway at the desired vehicle. Check out the top picture to the right. Within a typical 0.2 seconds, the reflected laser signal is detected by the laser gun, data is processed, and the gun alerts the policeman that he has the speed and displays that speed on the laser gun display.
Even if you had the best laser detector in the world, you can not detect and slow down in 0.2 seconds. For you Math challenged people that is 1/5th of a second, the blink of an eye! Six cars or more can be running in a pack, the laser beam can pass right by the lead vehicle, and the driver of the lead vehicle could have a radar detector in the windshield and he or she would not even know the laser beam passed their car. If the laser glances off a vehicle, it is possible that someone behind can get a laser alert, but again, it would not do any good. If you get hit with a laser gun, they have your speed in 1/5th of a second, unless you have a good laser jammer. But that is for another discussion, Technology 101, Laser Jammers.
As the laser beam travels down the highway, it looks like a picket fence. You remember, a series of white wooden pickets, separated by space, or in this case, saparated by "no light". Since light travels 186,000 miles a second in free space, (a little slower down here on planet earth), then we can not see the laser beam as it travels far too fast for the eye to see. In addition, the laser beam is at 904nm wavelength, and because our vision tops off around 725nm wavelength (deep red, also referred to as infrared), then even if the laser beam traveled slow, it is above our vision capabilities.
The beam, as described above, would look like a picket fence or a light train, traveling down the highway. A light pulse (light on), followed by a dark space (light off), followed by a light pulse, etc.; i.e, a picket fence. There are a series of these pulses traveling at light speed down the highway. As this light train stikes your car, it scatters a reflection back towards the laser gun, which also has a light detector. The laser gun knows when it transmitted each pulse, and measures the time it takes for each pulse to travel out and back. Time is relative to speed, and the vehicle speed can be quickly calculated. All of this is occuring in 1/5th of a second. The laser gun has to receive back a reasonable number of the pulses, before it can statistically calculate your speed.
The policeman often has to re-trigger twice with a laser gun to get the vehicle speed. If he aims up into the windshield, a portion of the laser beam will pass through the windshield and go out the back windshield. Depending on the rake (angle) of the windshield, if the laser beam were incorrectly aimed at the windshield, part of the laser beam will reflect up into space. No laser signal comes back and no speed would be indicated. However, most police are well trained in the use of laser. They don't aim at windshields, and they generally do not use the laser gun beyond 1000 feet in the USA. That rule is often not followed, especially in Europe, NZ and AUS. You need one of the best laser jammers to cause the laser gun speed display to go blank.