G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
G02B23/2407—Optical details
H—ELECTRICITY
H01—ELECTRIC ELEMENTS
H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
H01J37/3002—Details
H01J37/3005—Observing the objects or the point of impact on the object