The Study of Diffraction Grating Characteristics by Simplified Phase Contrast Methods

Abstract
The simple accessories required for studying spectroscopic apparatus, especially diffraction gratings, by this method may be mounted directly on existing instruments. The accessories are phase mirror, lens, and receiving unit. The examination is made using light from a strong spectral line. The receiving unit may be the eye, a photographic plate, or a photoelectric scanner. The results are interpreted in some detail. It is shown that a true phase curve of the wave front is obtained in so far as it is due to periodic structures inherent in the grating, so that the information is quantitative and accurate to better than λ/300. Random defects, important because they give rise to stray light, are revealed with less precision. As a result of the calculations, recommendations are made for the dimensions of accessories to suit different grating types. Examples of structures are shown.

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