Comparison of three methods for identifying fringe regions of interference fringe patterns in measuring gear tooth flanks by laser interferometry

Abstract In order to extract the fringe regions of an interference fringe pattern (IFP), which is of importance when measuring a gear tooth flank by phase-shifting laser interferometry, we introduce three simple methods without complex calculations, based, respectively, on gray filtering of individual IFPs collected in the phase-shifting field of 2 π , on subtraction between corresponding IFPs with the phase-shifting difference of π , and on an object – image pattern collected when the lights from the reference arm of the interferometer are hidden. And then they are attempted in a set of IFPs of a tooth flank of an involute spur gear, and their applicational results are compared. Last, advantages and disadvantages of the three methods are discussed, such as, (i) the sensitivities, the first and second methods to the nonuniformities, respectively, of the lights intensity and of the fringe density, and (ii) the immunity of the third method to the above problems, with the additional cost of collecting the object – image pattern when experimenting.