Three-dimensional Profile Measurement Of Human Head Based On Fractional Frequency-doubled Grating Projection

The 3-D profile measurement of human head were measured by the phase shift technique of fractional frequency-doubled projection grating.In this technique,several groups of grating with different spatial frequencies are inserted between two groups of grating with multiple spatial frequencies,this is the fractional-frequency-doubling grating which one has fractional multiple between the spatial frequencies.Fractional frequency-doubling grating phase shift technology can further solve the problem that due to the sudden change in the height of the object being measured,phase unwrapping could not be realized in the phase shift technique of integer multiple frequency grating.At the same time,it can avoid the period of the frequency-doubled grating is superimposed with that of the digital light modulator of the projector to cause the defects of moire fringe,so as to improve the measurement resolution.Therefore,compared with the phase shift technique of frequency-doubled grating,the phase shift technique of fractional frequency-doubling grating is more advantageous in restoring the object's three-dimensional morphology aspects,and the image details after 3-D reconstruction are more detailed and rich.In addition,the synchronous trigger device equipped with MC100 chip ensures the rapid and stable acquisition process,which provides an effective means for the measurement of three-dimensional morphology of human head.The main research content is as follows1.Write a computer program for fractional frequency-doubled projection grating.Draw different spatial frequencies sinusoidal gratings which are made by digital image technology for projection.2.Establish a 3-D surface shape measurement system for fractional frequency-doubled sinusoidal projection gratings.The array fractional frequency sinusoidal grating stripes are projected successively from the lower spatial frequency to the higher spatial frequency to the surface of the measured object,and the stripes are deformed with the fluctuation of the object surface.The digital camera is controlled by the synchronous trigger device,and the deformed stripes are collected into the computer synchronously.3.Write a computer program for the 3-D profile measurement of fractional frequency-doubled sinusoidal projection grating,and unpack the four-step transition fringe under the same spatial frequency.Starting from the package phase of the lowest spatial frequency,the expansion phase map is obtained step by step,until the expansion phase map of the highest frequency is obtained,that is,the relative height distribution image of the final three-dimensional shape of the human body.