US 11,788,927 B2
Evaluation of preforms with non-step-index refractive-index-profile (RIP)
Maximilian Schmitt, Duluth, GA (US)
Assigned to HERAEUS QUARTZ NORTH AMERICA LLC, Buford, GA (US)
Filed by Heraeus Quartz North America LLC, Buford, GA (US)
Filed on Feb. 26, 2021, as Appl. No. 17/186,907.
Prior Publication US 2022/0276124 A1, Sep. 1, 2022
Int. Cl. G01M 11/02 (2006.01); G01M 11/00 (2006.01)
CPC G01M 11/0228 (2013.01) [G01M 11/30 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A method for determining a radial refractive index profile of an object, the method comprising:
(a) providing the object, the object including a cylindrical optical object which has a cylinder longitudinal axis around which at least one layer k with a layer radius rk and with a layer refractive index nk extends radially symmetrically wherein the at least one layer is not step-index nor substantially step-index;
(b) measuring the deflection function of the object and transforming the measured data into a measured refractive index profile;
(c) assuming a refractive index level and radius for the layer of the object being evaluated and calculating a compensation level refractive index profile;
(d) generating a theoretical deflection function corresponding to the assumed refractive index level and radius and transforming the generated data into a fitting refractive index profile;
(e) comparing the fitting refractive index profile to the measured refractive index profile and evaluating the comparison against a predetermined accuracy level for the layer of the object being evaluated;
(f) repeating steps (c) and (d) iteratively until the predetermined accuracy level has been achieved;
(g) determining whether the object has another layer to evaluate and compensate;
(h) repeating steps (c) through (f) for each layer of the object until no further layers of the object remain to be evaluated and compensated; and
(i) calculating a measurement artifact compensated refractive index profile for the object by adding the measured refractive index profile to the compensation level refractive index profile and subtracting the fitting refractive index profile.