| 摘要 |
An error correction apparatus adapted for use with a longitudinal measuring instrument is disclosed. In the preferred embodiment the correction apparatus is mounted on a measuring instrument having a longitudinal scale, a scanning unit movable along the scale, and a housing surrounding the scale and the scanning unit. In measuring the relative position of two objects, the first object is connected to the housing and the second object is connected to the scanning unit via the correction apparatus of this invention. The correction apparatus includes a segmented correction profile made up of a plurality of individual correction members joined end to end to form a track extending substantially in the direction of the scale. The correction members are pivotably interconnected by joints which permit a limited amount of longitudinal movement between adjacent correction members. In this preferred embodiment each correction member is mounted on a shaft which is in turn eccentrically mounted on a rotatable disc secured to the housing. The position of the correction profile transverse to the scale can be adjusted by rotating these discs and the transverse position of the correction profile at any point is adjusted to correspond in a predetermined manner to the desired correction to be made. Pivotably mounted on the scanning unit is a lever arm which includes a roller on one end and an eccentrically mounted disc on the other. The lever arm is so arranged that the roller moves along the correction profile as the scanning unit moves along the scale, and the eccentric disc is positioned to determine the spacing between the second object and the scanning unit. As the lever arm pivots to follow the correction profile, the eccentric disc is rotated, thereby altering the separation between the scanning unit and the second object and introducing the desired error correction. |
