Accuracy improvement of full-field displacement measurement using digital image correlation for images obtained with a laser scanning confocal microscope

A method for image correction is proposed for digital image correlation in conjunction with a laser scanning confocal microscope (LSCM). The scan lines of an LSCM have sub-pixel error in their position in the scanning direction (drift distortion). Drift distortion decreases the accuracy of the displacement measured using the DIC method. The correction method proposed here removes both drift distortion and spatial distortion. Drift distortion is removed using a pair of images, each of which has a different scanning direction. Spatial distortion removal is performed using a methodology that employs a series of in-plane rigid body motions and a generated distortion map. Numerical simulations demonstrated that these correction procedures can successfully detect drift distortion. The standard deviation (SD) of the obtained detection error for artificial noise with sub-pixel line-shift was 0.004 pixels. Experimental results involving rigid body motion indicate that, after the correction of drift and spatial distortions, (i) the standard deviation of the measured displacements was 0.03 pixels, and (ii) the measured displacement fields are unbiased and agree closely with those obtained using an optical microscope. The proposed correction method effectively removes the distortions of obtained images and improves the accuracy of the digital image correlation method using an LSCM.