The Structural Optimization Design And Image Ouality Analysis Of Echelle Spectrograph

Laser-induced breakdown spectroscopy (LIBS), also known as laser-induced plasma spectroscopy (LIPS), belongs to the kind of atomic emission spectroscopy technology. It is a material element analysis technology and developed rapidly in recent years. Echelle spectrograph, the key components of LIBS,has a decisive effect on detection limit and precision of the LIBS. A portable principle prototype of echelle spectrograph is developed to meet the requirements of light, small, high resolution, high detection speed and high cost-effective in the practical application of the spectrograph.Echelle spectrograph uses the cross-dispersion structure. According to the system requirements, the dispersion form of the main dispersive element echelle matching with crosswise dispersive element prism is selected. Therefore, the unique design of autocollimator C-T structure of the echelle spectrograph is design, which combined Czerny-Turner with Littrow system structure. In the process of systemic optimization, aberration in the main dispersion and crosswise dispersion direction is analyzed by "calculation-simulation-correction" method. Using this method to reduce systematic aberration, and the system will be gradually improved until achieve the goal of structural optimization. The resolution is one of the most important criterions to evaluate spectroscopic instruments. It is quite necessary to analyze the main parameters in optical design to improve the imaging quality. Influence of the pinhole diameter, grating parameters, CCD pixel size, prism parameters are analyzed in this paper. It is found that the first three parameters are the main factors and then the mutual restraint relationship among these factors is deduced. It also can calculate limit pinhole diameter, so as to determine the characteristics of system parameters grating, prism, pinhole and CCD. Installation and alignment is an important stage to ensure optical system in optimal working condition. Therefore the center installation method is proposed to guarantee accurate adjustment of small range of each optical element’s stance and position. On this basis, the two-dimensional spectrogram of Hg lamp is got. The results show that portable high-resolution Echelle spectrograph we developed is able to meet with the requirements of other instruments (LIBS).