Dynamic measurement of 3D displacements using dual-camera lensless Fourier transform digital holography

Dynamic 3D displacement field measurement is an effective means to characterize the electrical performance stability and structural soundness of microsystems. Combining off-axis lensless Fourier transform multiplexed digital holography and multi-illumination profilometry, a dual-wavelength dual-camera optical setup with a multi-illumination system is developed to simultaneously acquire four phase images with different sensitivity vectors, as well as the object shapes. Meanwhile, the shared reference wave in off-axis lensless Fourier holography gives a convenient way for sensitivity vector modification and phase image registration, which are based on the stereo checkerboard calibration method. The dynamic 3D displacement fields and the strain maps of an energized integrated circuit board reveal that the inhomogeneous thermal expansion may cause some damage to chips, such as pin desoldering and microstructure fracture.