3D Profile Reconstruction of Solder Paste Based on Phase Shift Profilometry

Phase profilometry is an effective and efficient way to reconstruct 3D profile of objects through an optical method. It requires a pattern generator to project sinusoidal pattern onto objects. The deformed pattern is then captured by camera. However, noise from camera, distortion of lens, and imperfectness of projector cause trouble to the 3D profile reconstruction. It is necessary to filter the images before applying phase profilometry. In this paper, a 4-step phase shift profilometry (PSP) is used to reconstruct the 3D profile of solder paste. A 2D median and ID non-linear filters (pre-filtering) are proposed to filter the raw images. A 2D median and 2D non-linear filters (post-filtering) are used to filter out any parts which may be wrongly formed due to incorrect phase increment and non-ideal sinusoidal characteristic of projected pattern.