Segmenting the Valid Measuring Region (VMR) Based on the Local Density Estimation in Oblique Laser Interferometry
P-C. Yang, Y-Z. Dai, Y. Xiao, X-D. Zhu and X-H. Xia
Segmenting the valid measuring region (VMR) from an interferogram is an important step in the oblique interferometry, which is related to the final measurement accuracy. For the two interferogram defects which are the main sources of segmentation error, spurious fringes and defocused region on the boundaries of the VMR, a correction method based on local density estimation is proposed to improve the segmentation accuracy. First, a binary image based on the object image is generated as an auxiliary image in the following steps. Second, the pixels in high density region and low density region are determined respectively, and the boundary pixels are filtered based on the local density analysis. Third, the principles of selecting some parameters are summarized and the calculation steps are shown. To examine the correction method, the results of an experimental application of local density segmentation are given to verify the feasibility and accuracy. The two novelties in this work are: (i) The defocused region is considered and processed in segmenting the VMR; and (ii) a segmentation method which can reduce the impacts from the spurious fringes and defocused region at the same time is proposed.
Keywords: Laser interferometer, involute helical gear, local density estimation, image segment, gear tooth flank, valid measuring region (VMR)