Abstract: A microscope system for observing an image of a sample at desired magnifications includes a first objective lens having an objective side surface which is telecentric, a focusing lens, disposed in an optical path along which optical rays emitted from the first objective lens travel, for focusing the optical rays and forming a sample image and a second objective lens having a magnification factor different from that of the first objective lens. An interchanging member holds the first objective lens and the second objective lens and is used for placing one of the first and second objective lenses in an observational optical path between the sample and the focusing lens. The inequality 0.29<D/fI<0.40 is satisfied, assuming D to be a parfocal length which equals a distance between a surface of the sample and an attachment plane of the objective lens and fI to be a focal length of the focusing lens.

Abstract: A microscope objective lens has a modulator. The modulator can be rotated with respect to the objective lens to compensate for a change in orientation of the objective lens. This is achieved by providing various means on the objective lens for transmitting torque to the modulator, thereby rotating it.