Elevation and Windage adjustment is made through turrets located on the objective lens. Looking up through the objective lens revealed a giant blinking eyeball. After the electrons have left the sample they pass through the electromagnetic objective lens. A conventional microscope is used with a relatively small numerical aperture objective lens. O is collimated (made parallel) by a high quality objective lens. By 1812, Fraunhofer had succeeded in creating an achromatic objective lens in diameter. The stage is a platform below the objective lens which supports the specimen being viewed. Microscopes were first developed with just two lenses&colon; an objective lens and an eyepiece. It has a 30mm tube and has an objective lens diameter of 24mm. Light of the excitation wavelength illuminates the specimen through the objective lens. In two-photon excitation microscopy an infrared laser beam is focused through an objective lens. Objective lens diameter is typically in the range 20mm to 42mm. A typical telescopic sight objective lens has a focal length of .