Optical Design Of A Multi-object Fiber-fed Spectrograph System

Spectrum is one of the most important research fields in astronomy.As an astronomical spectral measuring instrument,the Multi-Object Fiber fed spectrometer is the most important scientific instrument for wide-field spectroscopic survey telescope.The optical performance of the Multi-Object Fiber fed spectrometer directly determines whether widefield spectroscopic surveys can achieve scientific purposes.However,for Multi-Object Fiber fed spectrometer,there are few optical design reports available for reference at present,and neither of them provide the calculation of Initial structure,nor optimize the constraints,which are very important information for the design process of optical system.Therefore,this paper establishes a set of multi-objective optical spectroscope design process including system performance index setting,initial structure building,system optimization process,performance evaluation,and completes a multi-objective optical spectroscope design scheme with good optical performance and processability,which will provide an effective reference for the design of other Multi-Object Fiber fed spectrometer optical systems.This paper presents an optical design of Multi-object and fiber-fed spectrometer with Volume Phase Holographic Gratings as the dispersion part.Based on the application requirements of spectral survey,we have formulated the optical performance indicators of Multi-object and fiber-fed spectrometer,and used them to build the multi-object and fiberfed spectrometer optical path and calculate the initial structure of each component.In the next overall optimization process,we use the geometric size of the spectral imaging area as the constraint for the overall optimization of the multi-objective optical spectrometer.While ensuring the good processability of the Multi-object and fiber-fed spectrometer,we also have a reasonable tolerance range and excellent optical performance.The design process is also applicable to the design of other multi-object and fiber-fed spectrometer optical systems with different number of channels,working bands and focusing lens structures.