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4 March 2019 New microcontroller unit improving stability and functionality of the optical chopper for atmospheric LIDAR
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Proceedings Volume 10925, Photonic Instrumentation Engineering VI; 1092518 (2019)
Event: SPIE OPTO, 2019, San Francisco, California, United States
The potassium LIDAR at Arecibo Observatory utilizes the Light Age alexandrite high power laser which requires a well synchronized system and steady trigger repetition rate to achieve correct height determination and to extend the lifetime of the equipment. The system includes an optical chopper that prevents the detector from saturating before the altitude of interest is reached and a sequence of delayed pulses that execute the laser trigger which are generated by an external pulse/delay generator. The accuracy of the optical chopper limits the accuracy of the laser repetition rate as well as other equipment in the synchronized system. This work describes the implementation of a new microcontroller based single instrument optical chopper and laser trigger controller to improve stability and functionality. By programming a unifying USB user interface, the new capability of monitoring the system and manipulating relevant variables was achieved. This includes changing the repetition rate, moving the optical chopper edge to block out different altitudes, tuning PID constants, and more. The new system centralizes control, increasing ease of operation and allowing more flexible and efficient use. Furthermore, a laser only mode for testing has been implemented to send out a laser trigger sequence to the rest of the system without the need of an optical chopper. The new implementation has reduced steady state frequency jitter of the laser trigger by 60% and startup time by 77%.
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Margaret M. Allard, Jens Lautenbach, and Luis Quintero "New microcontroller unit improving stability and functionality of the optical chopper for atmospheric LIDAR", Proc. SPIE 10925, Photonic Instrumentation Engineering VI, 1092518 (4 March 2019);

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