Research On Industrial Surveillance System Based On Pulsed Laser Scanning

The purpose of this work was to develop a laser scan system which can benefit from the improvement of single shot precision and measuring speed in laser ranging techniques. A small and compact optic system and brushless motor were also included.Design of the system was based on pulsed TOF laser range finder. A scheme of industrial surveillance system was proposed in this thesis. Through plenty of experiments the validity of the circuitry and optics was examined.A TOF laser range finder consists of a laser transmitter, one or two receivers and timing discriminators, and a time measuring unit. In order to improve single-shot precision the slew-rate of the measurement pulse should be increased, so the optical pulse of the laser transmitter should be narrower and more powerful and the bandwidth of the receiver should be higher without increasing the noise level too much. Pulsed laser diode was chosen as light source and APD/PIN as detector. The driving circuit can generate a pulse with a width of 15ns. An amplifier with JFET input stage and high bandwidth was selected to form a transimpedance preamplifier for PIN. To reduce the walk error caused by the changing in amplitudes of returning pulses, a practical timing discriminator was constructed which greatly improved the linearity in a range greater than 2m. The timing part consists of TDC-GP2 and DSP. In the experimental system, a precision of 2cm within 5m range was achieved and in the whole range, no worse than 10cm, good enough for surveillance and safety. At present, most of the domestic researches on laser scan system are confined in laboratories. Instruments designed were heavy. A small and compact optics was realized in this thesis, which made possible for producing lighter and more portable instrument. At last a simple and reliable motor scanning method was presented, which can ensure a scanning angle of at least 180°...