Patent ID: 8711473

Claim:
A focus adjustment unit used in a microscope system including an objective optical system that converts light from a specimen into a substantially collimated light beam and an imaging optical system that forms an image from the substantially collimated light beam of the objective optical system at a predetermined position, the focus adjustment unit being disposed between the objective optical system and the imaging optical system and configured to change the working distance of the objective optical system, in which a front side is defined as the side where the objective optical system is located and a back side is defined as the side where the imaging optical system is located, the focus adjustment unit comprising: a front-group optical system and a rear-group optical system that are sequentially disposed from the front side, each of the front-group and rear-group optical systems having refractive power; and a lens driver that drives the front-group optical system, the rear-group optical system, or both, along the optical axis direction to change the relative distance between the front-group and rear-group optical systems along the optical axis direction, wherein the front-group optical system is disposed such that its front focal point is positioned sufficiently proximate to the back focal point of the objective optical system to maintain a small gap distance between the back focal point and the front focal point, and a tip of the objective optical system is in physical contact with the specimen to minimize movement during observation of the specimen.