New to Typophile? Accounts are free, and easy to set up.
Ikarus, by Peter Karow and others of URW, is one of the most important historical font formats and font editing tools. In its heyday, it was the primary tool foundries used to digitize their libraries of metal and photo type. Today, Dutch Type Library offers IkarusMaster as part of their FontMaster suite of tools.
Ikarus had many technical strengths, including Interpolation, very high resolution, and a spline primitive edited using on-curve points, unlike the Beziers popular today, which also depend on off-curve control points.