Lens element from diamond-turned thermoplastic resin

A method for fabrication of a lens element comprising:

• a) shaping a lens blank from a high index, high thermal property thermoplastic resin;
• b) conditioning a surface of the lens blank by an extended annealing process comprising:
• i) increasing the temperature of the lens blank to a soak temperature greater than 165 degrees C. over a ramp-up period of more than 2.5 hours, increasing the temperature during the ramp-up period by no more than 2 degrees C. per minute, on average;
• ii) maintaining the lens blank at the soak temperature for a soak period of at least 3 hours;
• iii) lowering the temperature of the lens blank back to room temperature during a ramp-down period at a rate no faster than 1.5 degrees C. per minute, on average, forming a conditioned lens blank thereby;
• and,
• c) diamond-turning the conditioned lens blank to obtain an optical quality surface.