Abstract
A new type of controlled-diffuser consisting of a scalloped grating has been developed, and this leads to the design of a high accuracy integrating photometer, which can operate when the total light flux is below one microlumen. Both the theory and the details of preparation of a scalloped grating diffuser are given. An experiment illustrating the efficiency of the scalloped grating relative to other diffusers is described together with an experimental test on a particular design of integrating photometer.