| 摘要 |
PROBLEM TO BE SOLVED: To provide a radius of curvature measuring device in which a measure ment error at the peripheral part of a curved surface can be eliminated by measuring the central part and the peripheral part of the curved surface on conditions that the relative position thereof is constant. SOLUTION: The radius of curvature measuring device comprises a first optical system for projecting a central mark at a first angle with respect to the optical axis of an objective lens, a second optical system for projecting a central mark at a first angle disposed orthogonally to the first optical system, a third optical system for projecting a peripheral mark at a second angle larger than the first angle, a fourth optical system for projecting a peripheral mark at a second angle disposed orthogonally to the third optical system, and means for detecting the position of specific marks projected from first through fourth optical systems and reflected on a curved surface. A specific mark is projected through combination of one of the first or second optical system and one of the third or fourth optical system and the radius of curvature at the peripheral part of the curved surface is determined based on the position of the reflected images 41d and 42d of the mark.
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