Method for determining front and rear surfaces for optical patches

A method for determining a set of front patch surfaces and a set of rear patch surfaces for a series of optical patches each configured to provide optical power to a wearer of spectacles when the optical patch is combined with an eyeglass of the spectacles, the optical patch having a resiliency such that the front patch surface or the rear patch surface of said optical patch conforms to a shape of a posterior surface of the eyeglass,

• each optical patch being obtained by combining one of the front patch surfaces with one of the rear patch surfaces,
• each front patch surface being of pseudo-spherical shape, and each rear patch surface being comprised of a Fresnel structure superimposed on a pseudo-spherical base shape, pseudo-spherical surface denoting a continuous surface with curvature values existing at each point in the continuous surface,
• the series of optical patches containing at least one optical patch respectively for prescriptions each obtained by combining one optical power value out of a set of optical power values with one astigmatism value out of a set of astigmatism values,
• the method comprising the following steps:
• 1) providing at least one specification condition for the optical patches;
• 2) for a start-prescription, determining one first rear patch surface and one first front patch surface so that an optical patch obtained by combining said first rear patch surface and said first front patch surface meets the specification condition;
• 3) for each prescription within a prescription start-segment containing the start-prescription, and other than said start-prescription, calculating a secondary front patch surface so that an optical test patch obtained by combining the first rear patch surface with the secondary front patch surface corresponds to said prescription;
• 4) selecting a primary prescription sub-segment within the prescription start-segment, so that all optical test patches obtained in step 3 and corresponding to prescriptions within said primary prescription sub-segment meet the specification condition;
• 5) selecting a secondary prescription sub-segment within the primary prescription sub-segment, so that all prescriptions are contained in at least one prescription segment produced by a tiling based on said secondary prescription sub-segment, with each prescription segment being obtained by translating the secondary prescription sub-segment used as a tile in a plane with optical power and astigmatism coordinates;
• 6) for each prescription segment produced by said tiling, and for the prescription which is at a location with respect to said prescription segment similar to that of the start-prescription within the secondary prescription sub-segment, determining a secondary rear patch surface with Fresnel structure so that another optical patch obtained by combining said secondary rear patch surface with the first front patch surface corresponds to the prescription;
• and
• 7) assigning a rear patch surface and a front patch surface to each prescription in the following manner:
• 7a for the start-prescription, the first rear patch surface and the first front patch surface determined in step 2 is assigned
• when the prescription is within the secondary prescription sub-segment, and other than the start-prescription,
• the first rear patch surface determined in step 2 is assigned, and
• the secondary front patch surface calculated in step 3 for said prescription is assigned, and
• when the prescription is within a prescription segment produced by the tiling other than the secondary prescription sub-segment,
• the secondary rear patch surface determined in step 6 for said prescription segment is assigned, and
• the same front patch surface is assigned as the first front patch surface assigned in sub-step 7a or the secondary front patch surface assigned in sub-step 7b for the prescription within the secondary prescription sub-segment at the location similar to that of the current prescription with respect to the prescription segment.