Microscope comprising a focus error detecting optical system

摘要

A focus error detecting optical system (20) has an optical parameter which makes a focus lock-in range by a focus error signal (E) be a value capable of detecting focus on a front surface of a cover glass (52) and focus on a back surface thereof separately. A control section (3), based on the focus error signal obtained by the focus error detecting optical system (20), brings a focal point of an observational optical system (10) to a focus position. Further, focus error detecting optical systems (20) include optical units each having an optical parameter corresponding to a numerical aperture of respective objective lenses (11). A control section selects (3) the optical unit of the focus error detecting optical system corresponding to the objective lens (11) in use. The control section, using a focus error signal obtained by the selected focus error detecting optical system, brings a focal point of an observational optical system to a focus position.