| 摘要 |
An optical displacement measuring instrument includes a focusing unit (220) for bringing a focal point of an objective lens (170) into coincidence with a measuring face (901). The focusing unit splits reflected light reflected on the measuring face into two split light of first reflected light and second reflected light. The focusing unit includes: first and second light-receiving element arrays (237A, 237B) respectively disposed anterior to an image-forming point of the first reflected light and posterior to an image-forming point of the second reflected light; and a light-receiving signal calculator (focal-point detecting circuit (232)) that, among light-receiving signals from a plurality of pixels within an area predetermined in each of the first and second light-receiving element arrays, excepts light-receiving signals from pixels having the highest brightness to the nth highest brightness (n being an integer) and calculates the total value of light-receiving signals from the remaining pixels. A position of a focusing lens (130) is controlled such that the total values of the light-receiving signals of the first and second light-receiving element arrays become equal to each other, thereby bringing the focal point of the objective lens into coincidence with the measuring face. |
