Frenchy,

The original attempt was via a Photoshop filter and traced to vector in Illustrator, but a better result was had from http://jasondorie.com/downloads/HalftonerV1.5.zip

The halftone Photoshop filter is of course raster based.
HalftonerV1.5 allows one to save in DXF, so the 'dots' are generated indeed as circles.

And YES, HalftonerV1.5 is free.

Hope this helps.

-- Mindset

PS, I thank you Frenchy Pilou for all your considerable contributions to this forum as well