The consistent of laser pointing and theodolite tracking

Jia Wenwu; Zhang Sanxi; Lei Tao

doi:10.12086/oee.2020.190438

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Jia W W, Zhang S X, Lei T. The consistent of laser pointing and theodolite tracking[J]. Opto-Electron Eng, 2020, 47(9): 190438. doi: 10.12086/oee.2020.190438

Citation:

Jia W W, Zhang S X, Lei T. The consistent of laser pointing and theodolite tracking[J]. Opto-Electron Eng, 2020, 47(9): 190438. doi: 10.12086/oee.2020.190438

The consistent of laser pointing and theodolite tracking

1.
Chinese Huayin Test Center, Huayin, Shaanxi 714200, China
2.
Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, Sichuan 610209, China

Fund Project: Supported by Military Research on Weapons and Equipment Fund (012016018200A13302)

More Information

^*Corresponding author: Jia Wenwu, E-mail:jww4891@163.com

Received Date 24 July 2019

Revised Date 29 November 2019

Published Date 15 September 2020

Abstract

Abstract

The distance between the laser optical axis and the tracking optical axis of the theodolite (axis shift) and the parallelism error of the optical axis cause the tracking position of the theodolite to be inconsistent with the laser pointing position.The analysis of the influence of off-axis and parallelism errors shows that a large amount of shift and parallelism errors will lead to inconsistencies between the laser pointing and the theodolite tracking pointing, which in turn leads to an increase in the blind zone of the laser ranging, a decrease in the operating distance and the accuracy of target positioning. A dynamic correction method for laser pointing based on bias tracking is proposed. By keeping the target always at the center of the laser beam and keeping the laser ranging position consistent with the theodolite tracking and locking position, it effectively solves the effect of laser edge energy drop on the operating distance. For a certain type of theodolite, the blind spot of the target can be reduced from 1 km to 82 m. At the same time, in view of the problem that the bias tracking algorithm needs the initial distance of the target to start the bias tracking, a one-dimensional search method for the target with unknown initial distance is proposed, which greatly improves the search efficiency of the target with unknown initial distance. The method in this paper solves the problem of the consistency between the tracking position of the theodolite and the pointing position of the laser, and greatly reduces the limitation on the shift and parallelism of the laser optical axis and the theodolite tracking optical axis.
- single laser ranging thodolite /
- off boresight /
- parallelism eeror /
- bias tracking /
- one-dimensional search

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References

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Overview

Overview

Overview: As using laser ranger on theodolite to measuring the target's location in range test, it's common that the laser optical axis is a large distance (off-boresight) and weak parallelism with the tracking optical axis. It means that the location of laser pointing and the location of theodolite tracking is different. The influences of off-boresight and parallelism error are analyzed first. A broader off-boresight can cause larger ranging bind regions. The parallelism error may decrease the detecting distance when it corresponds to the laser divergence, and the laser pointing location is changing as the target moving, this decreases the accuracy of the location. It's common to decrease the off-boresight and parallelism error of the laser optical axis. But large off-boresight and parallelism error are unavoidable for some cases. A laser pointing dynamic correction method based on bias tracking is prompt to make the laser pointing the same with theodolite tracking. It keeps the target in the center of the laser beam by bais tracking other than in the center of the tracking field of view. As the laser is gauss distribution, the target in the center of the laser beam reflects more laser energy, this helps to increase the operating distance of laser ranger. It can decrease the blind region of the laser range greatly by changing the laser pointing and always aiming at the target. To a theodolite with 0.627°×0.470° tracking field of view and 590 mm off-boresight, it can reduce the blind region from 1000 meters to 82 meters. As the track locking location is the same with the laser pointing location, it helps to increase the location accuracy. When the original distance is unknown, it has to search the distance of the target. A one-dimensional search method for distance unknown target is prompted too. As it searches the target only in distance, it scans only a single line in the imaging field. So it can decrease the points of searching and improve the searching efficiency greatly comparing to traditional two-dimensional searching methods. For an imaging field of 3.7°×2.9° and searching step of 0.014°, it can reduce the scanning points from 258×202 points to 128 points. Thus by bias tracking and one-dimensional searching, the consistency of laser pointing and theodolite tracking is overcome. It releases the limits of off borsights and parallelism error to the laser optical axis and tracking optical axis. This helps to decrease the cost of theodolite, and is valuable to improve the accuracy of exterior trajectory parameters.