Patent ID: 7304282

Claim:
A fluorescent observation device including a focus detection system, the fluorescent observation device comprising: an objective lens for observation of a sample; a transparent member which has a refractive index that is different from a refractive index of the sample, and which meets the sample at a boundary face; an illumination optical system which projects illumination light via the objective lens to be totally reflected at the boundary face such that evanescent light is generated to excite the sample; an observation optical system for observation of weak fluorescent light emitted from the sample when the sample is excited by the evanescent light; a focus detecting optical system which projects focus detection light for auto-focusing on the boundary face via the objective lens; a dichroic mirror which is provided at the observation optical system, and which reflects the focus detection light and transmits the fluorescent light; and a detector which receives the focus detection light reflected from the boundary face, via the dichroic mirror; wherein auto-focusing is executed on the boundary face in accordance with a detection result of the focus detection light received by the detector; wherein the illumination optical system comprises an illumination light source which emits the illumination light and an illumination dichroic mirror which reflects the illumination light and transmits the fluorescent light emitted from the observation sample; and wherein the illumination light source emits laser light as illumination light, and the illumination optical system protects the laser light through an outer peripheral portion of the objective lens.