Flood-fill Phase Unwrapping Algorithm With Multiple Random Starting Points On A Curve Line

3-D profile measurement based on phase-shifting grating projection is widely applied in robotic vision system,3-D satellite map and human medical plastic surgery.By using the phase-shifting technology to obtain the wrap phase related to the object surface topography,the key to the successful implementation of this technology is unwrapping phase effectively to obtain the continuous phase distribution and then obtain the relative height distribution of the object surface topography.According to the cumulative error of the path dependence in phase unwrapping algorithm,flood filling algorithm is used to unwrap phase.A lot of starting points are selected randomly in the closed curve around the hole which would not be calculated.After the corresponding phase unwrapping of each starting point,the average value is obtained.This effectively reduces the path dependence accumulation error from both sides of the hole and greatly improves the accuracy and provides an effective method for better implementation of 3-D profile measurement.The main works are as follows:(1)The phase-shifting grating projection system is set up to measure 3-D surface.The sine grating fringes are projected onto the surface of a three-dimensional object and the digital camera takes the deformation of the fringe on the object surface.By changing the grating position,images of different phase are obtained.Then the wrapped phases related to the object surface topography are calculated by these phase-shifting images.(2)The algorithm of flood-fill phase unwrapping is programmed.Use the closed polygonal line to select the target area of the object and cut the holes in the target area.Then the flood-fill algorithm is used to unwrap the wrapped phases to obtain the height distribution of the object surface topography.(3)Selecting a lot of starting points randomly reduces the cumulative error of the path dependence effectively.After excluding the hole area on which the grating fringes projection cannot reach,establish a closed curve around it and select a lot of starting points on the curve randomly.Then calculate the average phases after unwrapping the phases.This method can effectively reduce cumulative error of the path dependence in the meeting point from both sides of the hole and greatly improves the measurement accuracy of 3-D profile measurement.