Patent ID: 6940641

Claim:
A fluorescence observation apparatus comprising: a light source; an illumination optical system conducting irradiation light from the light source to a specimen; an aperture member provided in the illumination optical system; a first wavelength selective member; a light splitter deflecting the irradiation light to conduct the light to the specimen; an objective lens interposed between the light splitter and the specimen; a second wavelength selective member transmitting fluorescent light emanating from the specimen; and a detecting device receiving the fluorescent light, wherein the aperture member has a partial aperture through which part of the irradiation light passes, and the fluorescence observation apparatus is provided with a projection optical system projecting the aperture member at a pupil position of the objective lens so that a size of the partial aperture and a magnification of the projection optical system are set to satisfy the following Conditions: 0.5 NA≦NA 1 <NA NA 1 <n where NA 1 is a numerical aperture derived from an angle made by a ray closest to an optical axis, of rays of light passing through the partial aperture, with the optical axis on the specimen, NA is a maximum numerical aperture of the objective lens, and n is a refractive index of a medium holding the specimen.