What is free-form Lenses?

Written by Optician Club on . Posted in Optician Tools, Progressive Lenses

Free-form is a manufacturing technology that allows cutting and polishing arbitrary surfaces
Numerically controlled generator and polisher
The surface does no longer need any symmetry
Surface defined in a sag file
Only limited by surface curvature: ~15 D

Characteristics of free-form progressive

Characteristics of free-form lenses

Is free-form more precise?

  • What is claimed: 0.01 D
  • Very difficult to achieve in plastic
  • Well tuned process with tools, soft pads and slurries not worn out, guarantees better precision than standard milling and polishing methods.


Has a free-form lens better optical quality?

  • Not necessarily.
  • Free-form is a manufacturing process, not a design method, neither an optical design software.
  • But free-form technology will allow you to get better optics, as far as you use good optical design tools.

Why there is so much expectation around free-form lenses?

  • The great thing around free-form is that ophthalmic industry is no longer tied to base-curve restrictions.
  • With standard base curves, a sophisticated lens must be made with a few complex surfaces (semi-finished blanks) and spheres or torus.
  • With free-form, each sophisticated lens may have its own sophisticated surface.

What is free-form Lenses


Why a different surface for each lens is better?

  • In Optics, asphericity is the way to correct for aberrations when you cannot use many lens elements.
  • In ophthalmic optics, compensation must be made by just one lens per eye.
  • Each prescription, each lens position, each object position, requires a particular asphericity to get the best possible correction.
  • Standard lenses uses the same asphericity for thousands of different situations: asphericity becomes useless.
  • A different surface for each lens will allow a different asphericity for each lens: optimum compensation of side effects (aberrations).

 

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