Wide nomenclature of modern industrial rigid endoscopes requires research into their optical specifics. The design of industrial rigid endoscopes has been considered. Endoscope optical system types are investigated, and their advantages and disadvantages are shown. Specific endoscope models manufactured by “VNIIMP-OPTIMED-1” Research and Development Centre are presented. Endoscope application examples are provided. The possibility of using domestic thin rigid endoscopes of various types for diagnostics is shown.