Measurement of eyepiece diopter of direct view imagers

This paper presents a detailed review on a present confused situation related to defining and measurement of the eyepiece diopter range of optical/electro-optical devices to be used for a direct observation by human observers. On the basis of this review three precise definitions of a direct view imagers eyepiece diopter are presented. One of these definitions is determined as optimal fit to describe the perception of human observers. Further on, design and measurement uncertainties of diopter meters are discussed and rules of accurate measurements are formulated. Finally, recommendations for the maximum acceptable errors of the diopter scale of eyepieces of classic types of direct view imagers are presented, as well.