Design and study of LAMOST reference fiber position measurement error compensation device

Accurate measurement of the position of the reference fiber is the key to ensure the positioning accuracy of the fiber, but due to the large aperture and large field of view of the LAMOST telescope, the diameter of its focal plate reaches 1.75m. The reference fiber is installed in the unit hole of the detection system as a reference. The reference fiber, which is the reference of the detection system, is installed in the unit hole of the focal plate, and the accurate detection of its position can only rely on the high-precision spatial measurement performance of the laser tracker. However, the systematic error of the laser tracker itself, as well as the temperature change and air flow in the environment have a large impact on the measurement results. This paper proposes a measurement error compensation device based on the relative position of spatial standard length rods, which consists of two or three indium steel rods with extremely small thermal expansion coefficients and accurately calibrated lengths as a reference, and the measurement deviations of the rod lengths and relative positions of the rods and the rods at the time of operation are related to the measurement errors of the reference fiber. According to the relevant algorithm, the position error of the reference fiber on the focal plane can be corrected in real time. Finally, experiments show that this device can effectively reduce the error of the laser tracker in the measurement of the position of the reference fiber.