Patent ID: 9625674
Date: 2017-04-18
CPC Classifications: G02B

Claim:
1. An autofocus device for a sample observation device provided with an objective, the autofocus device comprising: a photodetector that detects light; an autofocus optical system that includes a tube lens, guides light to one of two regions on a pupil plane of the objective that has been divided into two along an optical axis of the objective, and guides light that has passed through the other of the two regions after being reflected by a sample to the photodetector via the tube lens; and a light shielding member which is arranged between the tube lens and a light receiving plane of the photodetector and on which an aperture has been formed, wherein 2.1<ΦAP/(2·ΦLD) is satisfied where ΦAP represents an aperture diameter of the light shielding member and ΦLD represents a light flux diameter, on the light shielding member, of light reflected by the sample in a state in which the light is condensed on the light receiving plane by the autofocus optical system.