Patent ID: 7883209

Claim:
An apparatus for measuring a distance between components of an examinee's eye, the apparatus comprising: an interference optical system comprising: a light source that is arranged to emit low coherent light; a beam splitter that is arranged to split the emitted light into first split light and second split light; a projection optical system that is arranged to project at least one of the first split light and the second split light onto the examinee's eye; a photo-receiving optical system that comprises a photodetector and is arranged to synthesize the first split light that is reflected from the examinee's eye and the second split light to guide to the photodetector; and an optical-path-length varying optical member that is disposed on one of optical paths of the first split light and the second split light to be movable in an optical axis direction and is arranged to adjust a relationship between an optical path length of the first split light and an optical path length of the second split light; a position detection mechanism that is arranged to obtain a travel position of the optical-path-length varying optical member; and a calculation and control unit that is arranged to: control operation of a driving unit of the optical-path-length varying optical member to move the optical-path-length varying optical member toward a first direction of the optical axis direction and toward a second direction that is reverse to the first direction; obtain a first interference signal based on a first output signal from the photodetector, the first output signal being obtained while the optical-path-length varying optical member is being moved toward the first direction, and obtain a second interference signal based on a second output signal from the photodetector, the second output signal being obtained while the optical-path-length varying optical member is being moved toward the second direction; and calculate a plurality of distances between the components of the examinee's eye based on the travel position of the optical-path-length varying optical member where the first interference signal and the second interference signal are obtained.