Varied line spacing plane gratings have the features of self-focusing , aberration-reduced and easy manufacturing ,which are widely applied in synchrotron radiation, plasma physics and space astronomy, and other fields. In the study of diffracting imaging , the optical path function is expanded into maclaurin series, aberrations are expressed by the coefficient of series, most of the aberration coefficients are similar and the category is more, can't directly reflects image quality in whole. The paper will study on diffraction imaging of the varied line spacing plane gratings by using computer simulation technology, for a method judging the image quality visibly. In this paper, light beam from some object points on the same object plane are analyzed and simulated by ray trace method , the evaluation function is set up, which can fully scale the image quality. In addition, based on the evaluation function, the best image plane is found by search algorithm .
This paper researches the phenomenon of bi-grating imaging by the computer simulation. The process that white lights
are diffracted by two gratings with different space frequencies is simulated and the imaging characteristics are studied. A
bi-grating imaging relationship is given based on the simulation results. It agrees basically with the experiments.
Two gratings consist of an imaging system in which a clear virtual image of an object is formed. The diffraction
properties of gratings have important influence on the information of images. In this paper, the imaging characteristics
of bi-reflection, bi-transmission gratings system and the transmission-reflection grating system are studied. The imaging
process and the quality of images of three systems are compared and some characters are summarized. It is useful for
the deep understanding of bi-grating imaging effect and its new applications.
The comparison of bi-grating diffraction imaging and the displaying of ordinary transmission hologram with white light
source, shows two different imaging methods have same essence, but different characteristic. In these two processes of
imaging, the light-wave of the object has been diffracted twice, both methods have to combine the dispersed image of
different wave length, so both of them have to employ the spectral combination characteristic of grating. The bi-grating
imaging equation not only is fit for the bi-grating imaging process, but also has guidance meaning in ordinary
transmission hologram displaying with white light source and the aid of grating.