| 摘要 |
PURPOSE:To eliminate an influence of movement of a movable member along a linear traveling route upon the formation of interference fringes by providing a reflecting element in a linearity meter utilizing holography. CONSTITUTION:When a movable member 22 having a moving direction coincident with or parallel to an optical axis is shifted laterally, a hologram 23 is also shifted laterally so that linear interference fringes localizing on a screen 25 is produced. From this it is understood that a direction perpendicular to the line direction of the interference fringes assumes a displacement direction of the movable member 22. In this linearity meter, a light enters into the hologram 23 from an optical element 32, but its optical path length becomes constant irrespective of the position of the movable member 22 because reflecting elements 33, 34 are included in the optical path. |
