Analysis of LAMOST optical fiber positioning units closed-loop operation by dual-telecentric measurement system

Zuo, Jiale; Duan, Shipeng; Li, Mengtao; Liu, Zhigang; Hu, Hongzhuan; Wang, Jianping; Chu, Jiaru; Zhou, Zengxiang

doi:10.1117/12.2561446

Cited by 4 publications

(2 citation statements)

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“…In LAMOST, 4000 fiber units are almost evenly distributed over a 20-square-degree spherical coronal focal surface, while each of the fibers can be moved with two degrees of freedom by two motors. [1] In this case, it can observe and position 4000 targets simultaneously and locate the fibers accurately in accordance with the position of stars in a few minutes, greatly improving the observation efficiency. In order to ensure that there are no blind spots, it is necessary to overlap partly the observation areas of the fiber units, which may lead to collisions between adjacent units in the course of movement.…”

Section: Introductionmentioning

confidence: 99%

Optimization algorithm for anti-collision planning of fiber elements based on divide-and-conquer weighting

Liu²

2023

Advanced Optical Manufacturing Technologies and Applications 2022; And 2nd International Forum of Young Scientists on Advanced

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Lamost can precisely locate 4,000 optical fibers according to the star catalog position within a few minutes, which greatly improves the observation efficiency. There is no blind area, and the observation area of the fiber optic unit must be overlapped, but this will cause the adjacent units to collide during the movement process. Once the collision occurs, the observation accuracy and service life of the unit will be reduced. In order to solve the collision problem between optical fiber units, this paper proposes an anti-collision planning scheme for optical fiber units based on the idea of divide and conquer weighting. This scheme simplifies the overall collision problem into a small set of collision problems. The unit sequential is adjusted, and simulation experiments show that, compared with the commonly used path planning scheme, this method can better improve the observation efficiency of astrological phenomena and reduce the processing times of the unit.

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Section: Introductionmentioning

confidence: 99%

Optimization algorithm for anti-collision planning of fiber elements based on divide-and-conquer weighting

Liu²

2023

Advanced Optical Manufacturing Technologies and Applications 2022; And 2nd International Forum of Young Scientists on Advanced

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“…However, the precise position of the internal control points cannot be measured after the telescope is in operation. 19 To solve this problem, a fiber position measurement method based on the external planar target (EPT) is proposed in this paper. Using the external control points on the EPT instead of the internal control points, the EPT is flexibly assembled on the focal surface or disassembled, and the precise coordinates of the external control points distributed on the EPT are measured off-line, thus effectively avoiding the assembly error in the process of measuring the internal control points.…”

Section: Introductionmentioning

confidence: 99%

Fiber position measurement method in LAMOST based on external planar target

Zhang

Wang

et al. 2022

Opt. Eng.

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In the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project, the fiber should precisely align with the celestial target to obtain the spectrum of the star, and the position accuracy of the fiber in the focal plane directly affects the spectral quality. LAMOST uses photogrammetry to acquire the actual position of the fiber. However, the fiber view camera system without precise internal control points in the focal plane negatively affects measurement precision. To solve this problem, we propose a fiber position measurement method based on the external planar target (EPT) that replaces the internal control points with the external control points; multiview reconstruction and bundle adjustment with additional position constraints are used to calculate the position of the fibers. The validity of the measurement method is verified by the simulation and experiment. The preliminary results show that the method has good stability and the measurement accuracy of the fibers can reach 20 μm. Because the external control points are distributed on the EPT plane, the assembly error of the EPT and focal plane does not affect the measurement accuracy. Therefore, the proposed method can achieve precision measurement under nonprecision installation conditions.

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Novel Fiducial Fiber Scanning Measurement Method Based on a Polar Coordinate System for LAMOST

Zhang¹,

Chen²,

Liu³

et al. 2023

PASP

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The multiobject fiber-fed spectrograph is the core scientific instrument for large-scale spectroscopic surveys. For closed-loop control of fiber positioning, fiber metrology systems are implemented in numerous fiber-fed spectrographs. The position accuracy of the fiducial fiber in the focal plate directly affects the performance of the fiber metrology system. However, there are currently no suitable methods and devices for measuring the fiducial fibers with high accuracy in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). To solve this problem, this study proposed a novel online scanning measurement method for fiducial fibers in which a scanning camera was set up in front of the focal plate, and the rotation and translation movements of the focal plate were combined to set a polar coordinate measurement system. First, the pole and polar axis of the polar coordinate frame were determined, and the compensation values of the polar radius and angle of the polar coordinate of the fiducial fibers were solved in the field of view of the scanning camera. A prototype measurement platform was set up to verify the feasibility and scientific validity of the method. Experiment results show that the polar radius accuracy of the proposed method met the measurement requirements. The X–Y measurement accuracy can be further improved when a higher-precision rotary stage is adopted. Thus, the difficulties in online accurate measurement for fiducial fibers can be tackled by the proposed method with good operability in LAMOST.

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Analysis of LAMOST optical fiber positioning units closed-loop operation by dual-telecentric measurement system

Cited by 4 publications

References 0 publications

Optimization algorithm for anti-collision planning of fiber elements based on divide-and-conquer weighting

Optimization algorithm for anti-collision planning of fiber elements based on divide-and-conquer weighting

Fiber position measurement method in LAMOST based on external planar target

Novel Fiducial Fiber Scanning Measurement Method Based on a Polar Coordinate System for LAMOST

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