3-D Profile Measurement Based On Frequency-doubled Grating Projection

3-D profile measurement technology has been widely utilized in profile mechanical manufacturing and parts processing,human medical reshaping surgery,computer artificial intelligence and robot vision field.Via employing frequency doubling grating projection 3-D profile measurement technique,one can perform highly independent calculation at each sampling point of 3-D profile morphology which depends on the calculation results of adjacent points and thusly avoiding calculation path-dependent cumulative errors in phase wrapped operation of traditional single spatial frequency stripe phase shifting technique.FDGP method is approved with better accuracy on measurement and therefore,providing a feasible technique on 3-D profile measurement application.The main research work is as follows:(1)Wrote the computer program and drew the image of sinusoidal grating with different spatial frequency and the number of pixels to a multiple of the grating image for projection.(2)Established the 3-D profile measurement system with frequency-doubled grating projection.A series of spatial frequency-doubled sinusoidal grating bands were projected onto the profile of 3-D objects in order of time,forming a stripy image that changes with the profile of the objects.Digital camera synchronous acquisition system equipped with synchronous trigger device corresponding to the same time order were applied to film projection stripe images,which were used to calculated associated wrapped phase with 3-D object profile.(3)Developed the algorithm of the 3-D profile type measurement of the frequency-doubled grating projection same spatial frequency of four-step phase-shifting was used to calculate wrapped phase via step by step strategy,starting from the lowest frequency expansion phase,in order to achieve the expansion phase at highest frequency,which is the relative height distribution image of the 3-D profile of the object.In the calculation process,the spatial filtering algorithm is used to process the striated image and as a consequence,leading the smooth wrapped phase.The influence of the “bad point” area on the 3-D profile measurement is effectively reduced by eliminating the fringe shadow area and the high reflection point.