Passive vibration compensation in scanning white-light interferometry

We present a passive vibration compensation approach in scanning white-light interferometry (SWLI). A pointwise distance measuring interferometer (DMI) obtains fast temporal distance changes during the white-light depth-scan of an aerial-measuring Michelson white-light interferometer for topography measurement. Both interferometers share a part of the optical path so that the measurement spot of the DMI is within the field of view of SWLI. With the real positions of the interferometer with respect to the measuring object during the depth scan known from DMI measurements, we can compensate for the influence of unintentional distance changes caused by environmental vibrations or scanner nonlinearities. By reordering of the captured image frames and improved correlogram interpolation, we are able to reconstruct correct signals from completely distorted (and unusable) SWLI signals. Although the basic idea of the system already has been published, we improved the signal reconstruction technique so that the specimen's topography measurement can be obtained with the same accuracy as without any vibrations or scan distortions influence. In addition, we demonstrate the feasibility of the approach by different practical measurements with and without vibrations.