Micro Line is basically Audio Technica's take on a Micro Ridge, nobody holds a patent over the Micro Ridge name and for that reason Micro Ridge styluses from different manufacturers are not necessarily identical. Both profiles are very close in reality, the terms have been used interchangeably by the industry for decades, and both are also Van Den Hul derivatives.
AJ Van Den Hul was a physicist at Delft University of Technology in the Netherlands, who in the early 80s started it all by using CAD in an effort to build a stylus profile as close as possible to the shape of the cutting head, hoping to further reduce distortion. Both of these profiles are indeed of the "line contact" type, but quite different to the "fine line" ones, which are Shibata derivatives instead.
AJ Van Den Hul was a physicist at Delft University of Technology in the Netherlands, who in the early 80s started it all by using CAD in an effort to build a stylus profile as close as possible to the shape of the cutting head, hoping to further reduce distortion. Both of these profiles are indeed of the "line contact" type, but quite different to the "fine line" ones, which are Shibata derivatives instead.