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2025-01-27 03:41本頁(yè)面
【正文】 platform. In the latter case the rangefinder module is integrated with onboard thermal, night vision and daytime observation equipment. The most advanced military rangefinders can be integrated with puters. To make laser rangefinders and laserguided weapons less useful against military targets, various military arms may have developed laserabsorbing paint for their vehicles. Regardless, some objects don39。s path above the earth. These atmospheric distortions coupled with the divergence of the laser itself and with transverse winds that serve to push the atmospheric heat bubbles laterally may bine to make it difficult to get an accurate reading of the distance of an object, say, beneath some trees or behind bushes, or even over long distances of more than 1 km in open and unobscured desert terrain. Some of the laser light might reflect off leaves or branches which are closer than the object, giving an early return and a reading which is too low. Alternatively, over distances longer than 1200 ft (365 m), the target, if in proximity to the earth, may simply vanish into a mirage, caused by temperature gradients in the air in proximity to the heated surface bending the laser light. All these effects have to be taken into account. Calculation The distance between point A and B is given by D=ct/2 where c is the speed of light in the atmosphere and t is the amount of time for the roundtrip between A and B. where is the delay which made by the light traveling and is the angular frequency of optical modulation. Then substitute the values in the equation D=ct/2,D=1/2 ct=1/2 cLaser rangefinder A long range laser rangefinder is capable of measuring distance up to 20 km。 mounted on a tripod with an angular mount. The resulting system also provides azimuth and elevation measurements. A laser rangefinder is a device which uses a laser beam to determine the distance to an object. The most mon form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender. Due to the high speed of light, this technique is not appropriate for high precision submillimeter measurements, where triangulation and other techniques are often used. Pulse The pulse may be coded to reduce the chance that the rangefinder can be jammed. It is possible to use Doppler effect techniques to judge whether the object is moving towards or away from the rangefinder, and if so how fast. Precision The precision of the instrument is determined by the rise or fall time of the laser pulse and the speed of the receiver. One that uses very sharp laser pulses and has a very fast detector can range an object to within a few millimeters. Range Despite the beam being narrow, it will eventually spread over long distances due to the divergence of the laser beam, as well as due to scintillation and beam wander effects, caused by the presence of air bubbles in the air acting as lenses ranging in size from micros
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