The use of diffraction gratings as measuring elements on machine
tools is nowadays an accepted procedure. Part I of this paper therefore
sets out to give a brief understanding of the principles of diffraction
gratings, and the ways in which they have been utilised commercially.
In addition, comparisons are made with other reference elements and some
consideration is given to manufacturing techniques.
Part II of the paper deals in more detail with the pure theory of
crossed diffraction gratings.