Authors: Yang, S; Zhang, JY; Yang, YY; Huang, JY; Bai, YR; Zhang, Y; Lin, XC

RESULTS IN PHYSICS

Volume: 13 Published: JUN 2019 Language: English Document type: Article

DOI: 10.1016/j.rinp.2019.102201

Abstract:

We present a technique for compensating laser beam up-shifting induced by the hot air with temperature

gradient in a 2D-scaning laser radar for monitoring the intruder in the railway system, in which the

laser beam is scanning at a height only a few centimeters above the railway tracks so that any object

with a size of 5 cm x 5 cm x 5 cm or larger can be detected. It is found that when the laser beam is

traveling in the hot air with a temperature gradient, the direction of the laser can be up-shifted. The

up-shifted laser beam may miss the obstacle lies on the railway track and fail to detect and report the

accidence and it may eventually result in a disaster. The compensation of the upward shifting is

necessary to insure the normal operation of the radar system and it can be done by using the difference

in linear thermal expansion between metals, which produce an additional elongation when the temperature

changes. The temperature dependent elongation is used to drive a rotational stage, which rotates the

laser in the opposite direction against the up-shifting. The rotation of the stage compensates the

change of angle of the laser beam induced by the temperature gradient of the air. A prototype device is

constructed to test the idea. Without thermal compensation, the laser thermal shift can reach up to 15

mm when temperature changes 14 degrees C from 30 degrees C to 44 degrees C above the hot surface after

the laser beam travels 30 m and such a shift can be reduced to about 8 mm at the same distance when the

compensator system is used. The experimental data agrees very well with the theoretical calculation.6

Full Text: https://www.sciencedirect.com/science/article/pii/S221137971930600X