A method for high-speed three-dimensional measurement with low-speed camera is proposed. The spatial frequency encoded fringes are projected with high frame rate and deformed fringes are captured with low frame rate. Several fringes are integrated in one captured image. The directions and/or frequencies of these fringes are different. The spatial frequency spectrum of these fringes is separate in spatial frequency domain. So, the phases of different fringes can be obtained by filtering the image with different filters. Then several 3D shapes of different time are obtained from one captured image. The experiments are carried out to verify proposed method and measurement results are demonstrated. The method improves the speed of 3D shape measurement and reduces the cost of measurement system as well.
We proposed a cost-effective and full-field method for measuring vibration of loudspeaker using general industrial camera and fringe projection. The loudspeaker is excited by a sinusoidal signal. The fringe pattern is projected on the measured loudspeaker membrane that is dynamically deformed. Then the deformed fringes are captured by a camera. A trigger generation circuit is designed to control the camera. The Fourier Transform Profilometry (FTP) is adopted for 3D shape reconstruction. The validity of this method is approved by experiments. The cost of proposed measurement system is dramatically lower than that using high-speed camera.