CONDENSER LENS SYSTEM

PROBLEM TO BE SOLVED: To provide a condenser lens system capable of compensating aberration caused in accordance with the change of thickness of a slide glass and the deviation of image forming position (focus) in e.g. a microscope. SOLUTION: In the condenser lens system for forming the image of a light beam on a sample surface and illuminating through the sample surface, the condenser lens system has two lens groups. In order to compensate both the aberration of the condenser lens system caused in accordance with the positional change of the sample surface and the deviation of an image forming position, one lens group between two lens groups (L1, L2) is moved.