SHADOW CASTING METHOD FOR PROFILE MEASUREMENT

摘要

Apparatus (10) and method for determining critical dimensions of an object, using a light source (20) for propagating a non-coherent beam of light, which is collimated and propagated through a telecentric lens (30) towards a two-dimensional imaging device (32) for imaging the collimated beam of light. A viewing stand (40) situated between the collimator (22) and the telecentric lens (30), holds the object within the collimated beam of light, so that a silhouette of the object is obtained on the imaging device. A data processing means (16) coupled to the two-dimensional imaging device (32) for determining the critical dimensions of the object on the basis of its silhouette. An alignment unit (42, 44, 46, 50) is provided for aligning the object on the viewing stand, so that the silhouette of the object is nominally normal to the axis of the beam of light within a predetermined allowable tilt angle.