| 摘要 |
The thickness of a workpart (10) is measured to a high degree of accuracy by passing a coherent light beam (20) through an aperture (16) in the workpart (10). The aperture (16') can alternatively be created between an edge of the workpart (10) and an external reference plate (30). The light is diffracted on the far side of the workpart (10) and its diffraction pattern captured by a CCD camera (22). The captured image is analyzed by a computer (24) which compares the captured diffraction pattern to a stored referenced value to determine whether the thickness of the workpart (10) is within an acceptable range. The method is capable of returning measurements with micron or submicron resolution, and is a robust process readily adaptable to high volume production quality control applications.
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