Measurement of lenses' power based on moire deflection technology

A method of measuring lenses' power using Moire Deflection Technology is described. Starting from the definition of lenses' power and the principle of MDT, relationship between Moire fringes' tilting angle and the test lenses' power is deduced. Calculated result shows that lenses' power is linear with the tangent of Moire fringes' tilting angle. The corresponding calculating formula is given. Images of Moire fringes through a single lens, an aspheric lens and a progressive addition lens are provided. Measuring results of single lens's power using MDT are presented, and the relative measuring results using focimeter are given either. Meanwhile, comparison and analysis of the results are discussed. It shows that measurement of lenses' power using MDT has high precision and it is simple and convenient to implement. Furthermore, using MDT we can realize a whole measurement of lenses' surfaces, and this is very meaningful to lenses with their power various on the whole surface such as progressive addition lenses. Therefore, it is applicable and promising to test ophthalmic lenses using MDT.