Patent ID: 8408700

Claim:
A computer implemented method for calculating, using a processor, a customized progressive addition surface S′″ of a progressive addition lens (PAL) made of a material having an optical index of n, the method, comprising at least the successive steps of: a) providing N initial progressive addition surfaces where N≧1, each initial progressive addition surface, S k , where 1≦k≦N, being provided with characteristic data comprising: M k points, P k,i , where 1≦i≦M k , the sphere Sph(P k,i ), the cylinder Cyl(P k,i ) and the axe Axe(P k,i ) at each point P k,i the near vision point P k,nv , and the far vision point P k,fv , and selecting for each initial progressive addition surface S k a reference point P k,r among the M k points P k,i of each initial progressive addition surface, b) calculating, by the processor, N intermediate surfaces S′ k by flattening each initial progressive addition surfaces S k so as to have for each intermediate surface S′ k the value of the Sphere Sph(P k,fv ) at the far vision point smaller or equal to 1 diopter and the Sphere Sph(P k,nv ) at the near vision point smaller or equal to 1 diopter, c) calculating, by the processor, a transformed intermediate surface S″ by applying S ″ ⁡ ( P i ) = ∑ k = 1 N ⁢ ⁢ α k ⁢ T P k , r ; ɛ k ⁡ ( S k ′ ⁡ ( P i , k ) ) , where T p k,r ;ε k is an isotropic function applied to each point P k,i of each intermediate surface S′ k and α k a coefficient specific to each intermediate surface S′ k , each isotropic function T p k,r ;ε k is defined by the selected reference point P k,r of the intermediate surface S′ k , and a scaling parameter ε k , with ε k ≠1 when N=1, d) calculating, by the processor, the customized progressive addition surface S′″ by cambering the transformed intermediate surface S″ so as to have the desired value of the sphere in at least two points of the customized surface S′″.