To move forward in Lens Technology it is important to understand physics of light, technical optics and glass production.
Long before modern Endoscopy became a part of medical examination, Microscopy catalyzed tremendous advancements in biology and medicine. The most important scientists in 17th and 18th century were:
Light: Newton advanced theoretical knowledge of light and optics with his publication in 1704, Christian Huygens teached about the wave theory and Snellius about optical refraction.
Technical Optics: Design, optical calculation and production of optical systems is performed by opticians. Inventors: Gallileo Galilei, Johannes Keppler (telescope) Christian Huygens, Hans Lippershey, Antoni van Leeuwenhoek (Microscope)
Literature: Johann Michael Conradi: "The threefold Formed Viewing Beam"
For many of us it is surprising, that lens technology did not find the way from Microscopy, which was far ahaed, to Endoscopy at an earlier stage. But the answer is simple. As long as Lightening of a human cavity was not solved advanced Lens Technology was useless because of relationship between light intensity and Lens design. Therefore advanced lightening technology was in the focus of the inventors before they concentrated on Lens Technolgy.