Structure Optimal Design And Performance Impact Factors Analysis Of Integral Field Unit

Integral Field Unit(IFU)can obtain the three-dimensional spectral information of the target simultaneously through a single exposure.With the advantages of large field of view,high spatial resolution,high transmission efficiency and small volume,it has been widely used in astronomical observation.The Integral Field Unit in the form of "microlens array+optical fiber array" is to divide the field of view into several units by using microlens array.The microlens units correspond to the optical fibers of the optical fiber array one by one,and the outgoing optical fibers are arranged in turn in the slit of the spectrometer to realize three-dimensional spectral imaging.Optical fiber as the transmission medium of light,its parameters and transmission characteristics will affect the observation effect of the telescope.It is of great significance to optimize and design the overall structure of IFU and to influence the overall performance of IFU.Based on the optical theory of optical fibers and the focal ratio degradation theory of optical fibers,the overall structure of IFU is optimized and its performance is analyzed.Based on the analysis of the principle of microlens in IFU,the structure parameters of microlens array are optimized.The imaging quality of spherical microlens and non-spherical microlens at different wavelengths is analyzed by Zemax optical simulation software.The optimum structure is chosen,and the overall structure of the microlens array and the design of the close-packed mode are mainly concerned with the increase of filling ratio.According to the parameters of the microlens and the error limitation conditions,the minimum theoretical diameter of the core is obtained to select the appropriate optical fiber parameters.In order to protect the optical fibers,the overall structure of the microlens end is designed;the mechanical structure of the jack tool with high stability and adjustable position is designed,and the structure is optimized continuously in the process of assembling and verifying its feasibility;and the positioning method of the optical fiber at the microlens end is determined.Three error factors of misalignment between microlens array and optical fiber array are analyzed by three-dimensional alignment method.Based on Zemax's non-sequential ray tracing method,the optical path simulation model of microlens and optical fiber is established,and the distribution of optical fiber's outgoing spot is obtained when three errors exist alone.According to the principle of focal ratio degradation,the outgoing focal ratio and outgoing efficiency of optical fiber are calculated.The effects of three errors on the focal ratio degradation and transmission efficiency are analyzed.The transverse errors between 0 and 14?m have a greater impact on the transmission efficiency of the optical fiber,but have a smaller impact on the change of the focal ratio of the optical fiber;the longitudinal errors are less than 96?m,and the output energy and focal ratio of the optical fiber basically remain unchanged,while the angle errors will decrease when the error is greater than 96?m.The difference in the range of 0.115° has little effect on the output energy and focal ratio of the optical fiber.It is proved theoretically that the three errors in alignment process of micro lens and optical fiber are within the controllable range,which can meet the design requirements of IFU for optical fiber transmission performance.