The Hershey fonts are a collection of vector fonts developed c. 1967 by Dr. Allen Vincent Hershey at the Naval Weapons Laboratory, originally designed to be rendered using vectors on early cathode ray tube displays. Decomposing curves to connected straight lines allowed Hershey to produce complex typographic designs. In their original form the font data consists simply of a series of coordinates, meant to be connected by straight lines on the screen. The fonts are publicly available and have few usage restrictions. Vector fonts are easily scaled and rotated in two or three dimensions; consequently the Hershey fonts have been widely used in computer graphics, computer-aided design programs, and more recently also in computer-aided manufacturing applications like laser engraving.
The Hershey vector fonts used by IDL were digitized by Dr. A.V. Hershey of the Naval Weapons Laboratory. Characters in the vector fonts are stored as equations, and can be scaled and rotated in three dimensions. They are drawn as lines on the current graphics device, and are displayed quickly and efficiently by IDL. The Hershey vector fonts are built into IDL itself, and are always available.
A large amount of digital fonts is available for free on the web. One challenge with these fonts using a plotter is that the standard font formats (True Type .ttf and Open Type .otf) are defined by its outline. These outline paths are closed paths and the format require closed paths. When I use my plotter for writing text I will typically prefer to draw the centerline (single line) not the outline. The centerline is typically an open path and are therefore not accepted by the ttf/otf format.