Reseach Of Mosaic And Replication For The Echelle Grating

In the 1990 s,large-scale optical telescopes were built in many locations worldwide.High-resolution spectrometers were widely required for these telescopes,but the apertures of the available gratings could not meet the requirements of astronomy applications.There are two main methods of grating fabrication: mechanical ruling and holographic exposure,while the large-size grating is extremely difficult to manufacture with both of the methods.And it will expend specific human,material and financial resource,the success rate is really low.The mosaic echelle grating was then proposed.All major telescopes are equipped with a mosaic grating to increase their spectral resolution and satisfy the requirements for astronomical observations.In this context,the mosaic echelle grating will be researched including the mosaic method and the replication technology in this paper.Combining the mathematical relationships between the grating wavefront and surfaces with the spatial relationships between the two grating wavefront,a mathematical model of the mosaicking errors is established to mosaic gratings.The five-dimensional mosaicking errors will respectively be calculated.Then a mosaicking method for echelles is proposed.The ??zero-order‘‘ and diffraction-order interference fringes of the echelle can be imaged simultaneously on the detector using a mirror–echelle structure designed to remove the five-dimensional mosaicking errors.According to the mathematical model of the mosaic grating errors,the tolerance of the mosaic grating errors is given.In order to get a replica of the mosaic gratings,an angle adjustment structure of the interferometer is designed to meet the requirement of the incident light angle in the optical path of grating replication and mosaic.And the position error of the echelle is then analyzed.Then the mosaicking experiment is on the way.After the mosaicking experiment,the replication experiment of mosaic grating will be then carried out.The preparatory work has done before the replication experiment.The specific research work is as follows:Firstly,a mathematical model of the mosaicking errors is established to manufacture mosaic grating.The zygo interferometer will detect the wavefront of the two adjacent gratings,and each of the mosaicking errors will be calculated by analyzing the spatial relationships between the fitted planes for the wavefront.According to the calculated values of the mosaicking errors,the compensative effects of the mosaicking errors will be eliminated,and the movement data of the adjustment mechanisms can be confirmed.The mosaicking errors can be analyzed quantitatively and the experiment will be succeeded more effectively.Secondly,based on the characteristics of the echelle,an interference method that is suitable for mosaicking echelles is proposed in this work.To avoid low zero-order efficiency,we design a new structure called the mirror–echelle structure to image simultaneously the ?zero-order? and diffraction order interference fringes,the five dimensional mosaicking errors are divided into two categories for elimination using the ??zero order‘‘ and the diffraction order.A theoretical model of echelle mosaicking is established,and the steps of the mosaicking experiment are summarized.Thirdly,according to the structure of the mosaicking error detection system of the echelle,the error angle of the incident light is analyzed,the design criterion of the supported structure which adjust the interferometer is given.And the rotation parameters for the adjustment mechanisms of the mosaicking errors are calculated again,when the rotation center is not overlapping with the original point.Then the position error of the echelle is analyzed,the measurement accuracy of the echelle position is given.The tolerance of mosaicking errors is calculated.Fourthly,the preparation work of the replication experiment for the mosaic echelle is carried out.The influence of the coating on the diffraction wavefront is analyzed,and then the curing experiment of the normal temperature glue is carried out,and the curing time of the normal temperature glue is given.Fifth,the mosaicking experiment is carried out as the above description.By using the zygo interferometer,the mosaicking experiment is set up with two echelles,where the pv values of the two echelles are 0.494? and 0.452?.The adjustment mechanisms are moved in accordance with the calculated mosaicking errors.We finally obtain a mosaic echelle with the pv value of 0.545?.And the replication experiment is then following.