Abstract: Bat wings are removed at step discontinuities within the coherence length of the light source of a vertical-scanning interferometer. A first height profile is obtained from a correlogram using a coherence-sensing technique. A second height profile is obtained from phase measurements at the best-focus frame position of the scanner. The two profiles are compared, and phase ambiguities are removed in conventional manner. In addition, during unwrapping the differences in height between two adjacent pixels obtained both by coherence sensing and by phase measurements are compared to f&lgr;/4. Where the inter-pixel height difference calculated by coherence sensing is smaller and the inter-pixel height difference calculated by phase is larger than f&lgr;/4, the phase measurement is corrected by 2&pgr; increments until both coherence and phase inter-pixel height differences are within f&lgr;/4. This additional step removes bat-wing effects from profiles obtained by phase measurement.

Abstract: Bat wings are removed at step discontinuities within the coherence length of the light source of a vertical-scanning interferometer. A first height profile is obtained from a correlogram using a coherence-sensing technique. A second height profile is obtained from phase measurements at the best-focus frame position of the scanner. The two profiles are compared, and phase ambiguities are removed in conventional manner. In addition, during unwrapping the differences in height between two adjacent pixels obtained both by coherence sensing and by phase measurements are compared to f&lgr;/4. Where the inter-pixel height difference calculated by coherence sensing is smaller and the inter-pixel height difference calculated by phase is larger than f&lgr;/4, the phase measurement is corrected by 2&pgr; increments until both coherence and phase inter-pixel height differences are within f&lgr;/4. This additional step removes bat-wing effects from profiles obtained by phase measurement.

Abstract: The process of combining various sets of measured data is carried out by first selecting a section of the test surface and its data set as the starting point and comparing the regions of overlap with adjacent sections of the test sample. All pixels containing an invalid data point in at least one of the data sets of each overlapping region are eliminated from consideration and the remaining valid pixels are counted. Then the adjacent section having an overlapping region with the largest number of valid pixels is selected for combination with the first section and their data sets are fitted according to a predetermined procedure, thereby producing an enlarged composite set of corrected data. The process is then repeated by comparing the overlapping regions of all sets adjacent to the composite section to determine the one having the largest number of pixels with valid data points. That set is then fitted to the existing composite profile to produce a new composite set of corrected data.