Design And Evaluation Of The Progressive Addition Lenses

Progressive addition lenses (PAL) is a new kind of effective solution to presbyopia, it has many advantages over other lenses dealing with presbyopia. Investigation of its design and evaluation method is shown in this dissertation.Firstly, various kinds of presbyopia lenses is reviewed and compared. The basic feature and principle of the PAL are introduced and the difference between the characteristics of hard design and soft design is described as well.Next, the soft method based on the Dirichlet principle is given in detail. Emphasis is put on the pattern of power addition along its main meridian line and the construction of the envelope of the nonrotationally symmetrical aspheric surface. From the monotonicity of the power addition along the central meridian line of the surface, methods for selecting the design parameters is discussed.Then, according to the differential geometry theory of curving surfaces, PAL's performances are evaluated. And, the methods for assessment of the lenses with ray-tracing software are provided.Finally, as examples, several kinds of PAL with 2.50m-1 addition are designed. It is shown, through the analysis of their surface power and astigmatism, that the shape of the meridian line has significant influence upon the distributions of surface power and astigmatism. Their keystone distortion is small. In this way, PAL meeting different circumstances can be designed.