A differential absorption lidar (DIAL) using a Q-switched CO(2) laser and a heterodyne receiver has been developed. The DIAL system is highly automated with computer-controlled laser-line selection and signal processing. The transmitter operates at a pulse-repetition frequency of 20 kHz and has an average output power of 1.8 W. A wideband HgCdTe detector is used together with a high speed adding buffer to detect the return signals. The system has been used in a field experiment to monitor ethylene emission from a petrochemical factory.
This paper describes some general features of a computercontrolled laser system for noncontact measurements of dimensions of objects. The laser beams are scanned over the object and a system of detectors mounted behind the object detects whether the beams are shadowed by the object or not. The detector signals are converted to digital values and transferred to a minicomputer, where they are processed. This may require special software to allow the dimensional data to be presented in real time. An experimental system with a HeNe laser and controlled by an HP 21MX minicomputer has been built and tested. At a rate of 100 measurements per second the systematic error is in the order of 1 mm for absolute measurements and 0.1 mm for relative measurements. The imprecision is about 0.1 mm for both cases.
AbstractThis paper describes some general features of a computercontrolled laser system for noncontact measurements of dimensions of objects. The laser beams are scanned over the object and a system of detectors mounted behind the object detects whether the beams are shadowed by the object or not. The detector signals are converted to digital values and transferred to a minicomputer, where they are processed. This may require special software to allow the dimensional data to be presented in real time. An experimental system with a HeNe laser and controlled by an HP 21MX minicomputer has been built and tested. At a rate of 100 measurements per second the systematic error is in the order of 1 mm for absolute measurements and 0.1 mm for relative measurements. The imprecision is about 0.1 mm for both cases.
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