| 摘要 |
A surveying instrument having a sighting optical system and a phase-difference detection type focus detection device which detects a focus state of the sighting optical system from a correlation between a pair of images respectively formed by two light bundles which are respectively passed through two different pupil areas on an objective lens of the sighting optical system, the phase-difference detection type focus detection device includes a pair of line sensors, a condenser lens group for condensing the two light bundles which are respectively passed through the two different pupil areas, and a pair of separator lens groups for forming two images of the two light bundles which are passed through the condenser lens group on the pair of line sensors, respectively. The condenser lens group includes more than one sub lens group.
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