Richard W Swinford

US Patent:

6552806, Apr 22, 2003

Filed:

Feb 3, 2000

Appl. No.:

09/497567

Inventors:

Richard W. Swinford - Tucson AZ
David J. Aziz - Tucson AZ
Bryan W. Guenther - Tucson AZ
Paul R. Unruh - Tucson AZ

Assignee:

Veeco Instruments Inc. - Tucson AZ

International Classification:

G01B 902

US Classification:

356512, 356497

Abstract:

Average fringe contrast is determined by PSI measurements at each step of relatively large translations of the reference optics and mirror of a white-light Linnik interference objective and the resulting data are used to minimize the OPD between the reference and test beam paths of the instrument. Utilizing the same algorithms used in the art to perform conventional vertical scanning interferometry, the position of minimum OPD is determined by finding the position of maximum average fringe contrast. Furthermore, by automating the system with a precise translation mechanism, operator-to-operator variations are completely eliminated and the precision of the process of OPD minimization is greatly improved. In another embodiment of the invention, the optimal focal position of the reference mirror is found at the same time by calculating the average lateral variation of fringe contrast as a function of OPD and focal position. The optimal OPD and focal position correspond to the maximum average lateral variation of fringe contrast in the resulting three-dimensional space.