Patent ID: 7304789

Claim:
A microscope system comprising: a light source; an objective unit including: an objective optical system for focusing light emitted from the light source onto a specimen, the objective optical system including a small-diameter distal optical system arranged at an end that is brought near to or into contact with the specimen; a threaded mount provided at a coupling position; and an outer cylinder enclosing the small-diameter distal optical system; an imaging optical system for forming an image of light that is emitted from the specimen and passes through the objective optical system; a microscope main body for housing the imaging optical system, the objective unit being detachable from and attachable to the microscope main body with the threaded mount at the coupling position; a light-scanning unit for scanning excitation light from the light source onto a surface of the specimen; a pupil-projection optical system disposed between the light-scanning unit and the imaging optical system to project a back focal position of the objective optical system near the light-scanning unit; a collimating optical system for focusing light that passes through the pupil-projection optical system; and a photodetector for detecting light focused by the collimating optical system, wherein the light source includes a laser light source; wherein conditional expression 0.15≦Lm/Lp≦0.5 is satisfied, where Lm represents the distance from the coupling position of the objective optical system to a position of the intermediate image along an optical axis, and Lp represents the distance along the optical axis from the coupling position to a position that has a conjugate relationship with the back focal position of the objective optical system through the imaging optical system and the pupil-projection optical system; and wherein conditional expression Df/Da≦0.3 is satisfied, where Df represents the outer diameter of the outer cylinder and Da represents the outer diameter of the threaded mount.