Patent ID: 7643208

Claim:
An optical scanning observation apparatus comprising: a light source configured to emit illumination light for illuminating a sample; an objective optical system configured to focus illumination light from the light source onto the sample; a detection-light splitting device configured to split off, from the illumination light, detection light emitted from the sample and collected by the objective optical system; a detection-light focusing optical system configured to focus the detection light split off by the detection-light splitting device; a detector configured to detect the detection light focused by the detection-light focusing optical system; a focus scanning device configured to be capable of being inserted and removed, disposed between the detection-light splitting device and the objective optical system, and a transverse-direction scanning device disposed between the focus scanning device and the objective optical system and configured to scan the illumination light from the light source on the sample in substantially orthogonal directions with respect to an optical axis, wherein the focus scanning device includes a focusing optical system formed of at least a positive lens group and a negative lens group, and a lens driving device configured to move at least one lens group included in the focusing optical system in the optical-axis direction to change a working distance of the objective optical system, wherein the positive lens group and the negative lens group are driven close to a positional relationship in which the overall focusing optical system forms an afocal optical system, and wherein absolute values of focal lengths of the positive lens group and the negative lens group are substantially the same.