The LEN file format is the file format of the OSLO lens design program.
Existing lens designs are always a good source of ideas and starting points for new lens designs. A treasure trove of lens designs is the collection of OSLO lens files from Bruce Walker.
Import of LEN files into LensForge is still quite rudimentary: the files must describe rotationally symmetric designs and aspheres are not supported (but conicoids are). We can expand the import capability quickly depending on feedback from our customers. If you have an OSLO LEN file and would like to know if LensForge will read it, feel free to contact us.
Here is a eyepiece design from the aforementioned treasure trove:
And here is how it looks in LensForge without any massaging of the lens data:
See also: