Research On The Measurement Method Of Grating Diffraction Efficiency Based On Fourier Optic Principle

Diffraction efficiency, as one of the most important performance properties of diffraction grating, directly determines energy transmission characteristics of spectral instruments. Its measuring results can give guidance to grating fabrication technology and to accuracy analysis of grating ruling engine. Whatever for makers or users of grating, it is very important to research and develop high-accuracy measurement devices of grating diffraction efficiency. Generally, it uses the double monochromatic structure to measure the diffraction efficiency,but traditional double monochromatic measurement method of diffraction efficiency for plane grating involves two major problems, the one is the differences of output spectrum bandwidths during measuring standard reflection mirror and the tested grating, the overlapping of diffracted spectra and the scatter light in the instrument., which influence the testing accuracy of diffraction efficiency, and the other is the model of one time testing can only measurement a single wavelength of grating efficiency, which reduced the efficiency of grating measurement. In this paper, a new measuring method of relative diffraction efficiency based on Fourier optic principle is presented. We deeply study the measurement method of grating relative diffraction efficiency based on Fourier optic principle and the main work is as follows:First, combining with the principle of Fourier optics and traditional measurement method of grating diffraction efficiency, we present a new measuring method of relative diffraction efficiency based on Fourier optic principle. The mathematical model of diffraction efficiency is deduced and the software simulation verifies the correctness of above theory, the measurement condition and advantage between our method and the traditional one is discussed at the end;Second, the influences of the moving cube corner’s tilt error, lateral shift error,maximal moving distance error, the aberration of the new system and sampling error on the measurement accuracy are analyzed in detail using the theory of optical trace and Fourier optics The analyses provide theoretical references for designing diffraction efficiency instrument;Third, we complete the design work of our diffraction efficiency instrument which include three main jobs: Firstly, we analyze the influence of stability of the source radiation on the testing result and then design the source system; Secondly, the front interfere system is devised through the analysis of the size of entrance slit, the surface of the optics component; In the end, we complete the design of the measurement monochromatic using the traditional offset aberration method;Forth, the alignment of our diffraction efficiency instrument is completed using the spot target and observing of the interference pattern method. The system of measuring control and data processing is also developed at the meantime;At last, the alignment and the measuring control program is perfected by some experiments, a improve program to increase the performance of our instrument is presented, the contrast experiment between the original program and the improved plan is done after that. In the end, we finish a series of experiments to test the performance of the improved instrument and the result shows that our method and the design, alignment, calibration of the instrument based on our method is both correct and effective.