Spatial resolution and accuracy

VIC-3D Pro­fes­sion­al Sys­tems deliv­er full­field, high­ly accu­rate shape, motion and defor­ma­tion mea­sure­ments. Lim­its can be traced for indi­vid­ual setups by sim­ple pro­ce­dures out­lined in the VDI-2626 direc­tive espe­cial­ly devel­oped for dig­i­tal image cor­re­la­tion (DIC). This exam­ple shows prin­ci­pal strain ε1 and ε2 (click to start video). In cas­es with local high peaks, a high spa­tial res­o­lu­tion can be the key to achiev­ing pre­ci­sion and accu­ra­cy for peak strain, in addi­tion to excel­lent SNR and cal­i­bra­tion of VIC. Video gen­er­at­ed with­in VIC iris work­space by isi-sys.


A high opti­cal res­o­lu­tion com­bined with suit­able speck­le size and den­si­ty is not only required to resolves the spa­tial strain dis­tri­b­u­tion as in the case before, but also improves accu­ra­cy in par­tic­u­lar for strain peak deter­mi­na­tion (upper right sketch), due to the fact that sub­set and strain fil­ter sizes (in pix­el scale) are fur­ther reduced (in absolute scale) com­pared to the peak strain dis­tri­b­u­tion. This fact also mat­ters for strain gauge size, as they are also not point strain mea­sure­ment device but inte­grat­ing over their length. The low­er right image is zoomed down to the pix­el  size range in VIC. It shows a high end case using the Blue-Fal­con. The lit­tle grey val­ue squares (two marked green) cor­re­sponds to the inten­si­ty val­ue of a pix­el and cov­er an area of 1.83 μm2. The vis­i­ble speck­le diam­e­ters are in the range between 3 to 8 pix­el. The red and yel­low squares also indi­cate the pix­el size oper­at­ing with larg­er FOV (mag­ni­fi­ca­tion 1:7 and 1:14), which would even not resolve speckles.