Research On Three Dimensional Sensing Of Small Object Shape Base On Fourier Transform Profilometry

The optical three-dimension profilometry measurement technology is more and moreimportant in the domain of machine vision, industrial inspection, quality controllingand medical science, etc with many advantages such as: non-contact measure, highaccuracy and sensitivity, automation. Appearance inspection and accessoryprofilometry precise measurement is more and more important in industrialproduction, shape measurement as a useful automatical technology is used widely,especially on occasional that same object is hard to measure or small objectmeasurement.The mathematical model of FTP phase measurement method is analyzed. Therelationship between the phase and the height is researched. When the measured smallobject shape is complex or polluted by noise, frequency spectrum distribution ismixed, causes unable accurately to restore the three dimensional shape. Fouriertransform profilometry based on two-dimensional wavelet transforms of imageprocessing is used and one piece of deformed strip image is needed, the backgroundimage is created by carry on the two-dimensional wavelet transform. The spectrum ofbackground component in deformed strip image is basically removed and the usefulspectrum is leaved easily. With this algorithm, the design demand for filter is low,frequency spectrum mix is prevented and survey scope is improved.The system adopts digital fringe projection techniques and its measurement hasadvantages of non-contact, the whole field, higher precision and quite high speed. Intraditional measurement systems, the fringe patterns are usually obtained through thephysical grating. However, the system adopts the digital fringe projection system toproduce the standard sinusoidal projection fringe with the high ratio of light andcontrast by a computer, the period and pattern of grating is changed according to thegeometry form of small object is measured. So tradition various errors is avoided withstrong adaptability and simple operation, thus raises the ratio of resolution of thesystem and precision of the measurement, experiments show that good results isobtained using structured light method to measure three-dimensional profile. At last,the image processing and system errors are analyzed.