Laser Interferometry Hologram Registration for Three-Dimensional Precision Measurements

Abstract

A hologram registration method is developed for the laser holographic interferometry measurement of the 3D surface profile of objects which are larger than the field of view (FOV). The theory of laser holographic interferometry, including the phase-shifting and multiwavelength tuning, is described. The hologram registration without using targets is elaborated. The cross-correlation analysis is used to find the translation and overlapped regions, which determine the tilt and shift correction for data registration. The proposed method is validated using two examples with different approaches. The first example, a wheel hub, is smaller than the FOV and demonstrates only 0.1μm discrepancy of the surface flatness between the registered and standard measurements. The second example, an engine combustion deck surface, is larger than the FOV. The registered surface measurements are compared to that of coordinate measurement machine (CMM) with only 2.5% discrepancy of the peak-to-valley flatness. This data registration method enables the sub-μm precision and large depth of field (several centimeters) measurement of large size objects.