Circular and spiral diffraction gratings

Abstract
The optical properties of gratings consisting of equally spaced concentric circles or spirals are considered and their image-forming properties are described. Expressions for the light intensity distribution in the images of a point source are derived. Examples of the use of such gratings for metrological and other purposes are indicated, together with the order of precision obtainable. The accuracy of construction of gratings for such purposes is very high, and methods for achieving this accuracy are described.