A method for surfacing a lens blank with a cutting tool

A surfacing machining for surfacing a blank to obtain a surface of an optical element by cutting a blank with a cutting tool of the surfacing machine, the system comprising

• a cutting tool to cut the blank to obtain a surface of an optical element,
• a computer, and
• a computer program product comprising a series of instructions,
• wherein said instructions, when loaded in the computer, are capable of implementing the steps of a method for determining a compensated surface description data intended to be loaded into the surfacing machine,
• the method comprising:
• providing a surface description data,
• the surface description data representing the surface of the optical element;
• providing contact data from the surface description data,
• the contact data representing the contact points to obtain with the cutting tool
• the surface represented by the surface description data,
• the contact point being the contact point between the cutting tool and the surface of the blank to obtain the surface of the optical element, and
• the contact point being defined in a cutting tool coordinate system;
• generating a compensation map by using a transfer function,
• the input of the transfer function being at least the contact data and the output of the transfer function being the compensation map;
• determining a compensated surface description data from the generated compensation map and the surface description data.