Fig. 1
From: Improved 3D measurement with a novel preprocessing method in DFP
Comparison between dark background and white background. a One of captured fringes on the object with dark background, b modulation distribution of the captured fringes, c modulation histogram, d one of the captured fringes on the object with a white background, e modulation distribution of the captured fringes, f modulation histogram. In f, the lower threshold t 1 is for shadow and interior invalid points detection, and the upper threshold t 2 is for background detection