Sub-pixel detection of laser-induced damage and its growth on fused silica optics using registration residuals

Abstract

Fused silica optics are key components to manipulate high energy Inertial Confinement Fusion (ICF) laser beams but their optical properties can be degraded by laser-induced damage. The detection of laser damage sites is of major importance. The challenge is to monitor damage initiation and growth at sub-pixel scale with highly sensitive measurements. The damage diameter is a widely used indicator to quantify damage growth but its accuracy is strongly dependent on the available image resolution. More recently, it was shown that registration residual maps (i.e., gray level differences between two registered images) could also be used to monitor laser-induced damage. In this paper, the performance of both indicators are compared to detect laser damage initiation and growth at high and low image resolutions thanks to a highly instrumented laser setup. The results prove that registration residual maps are more efficient to detect sub-pixel laser damage growth than diameter measurements at a given image resolution. The registration residual maps are therefore a powerful indicator for monitoring laser-induced damage initiation and growth at sub-pixel scale either for laser damage metrology setups, for high energy laser facilities, or other situations where damage is suspected to occur. The accuracy of (laser-induced) damage laws may also be improved thanks to this tool.

Characterization of glass fiber reinforced polymer via digital volume correlation: Quantification of strain activity and damage growth

“…3(d)). If damage did occur, it remained very low and at a scale lower than the scan resolution [30]. Second, the first cracks initiated and propagated near the unnotched specimen ligament edge, in spite of high strain gradients in the notched region.…”

Damage Detection in a Polymer Matrix Composite from 4D Displacement Field Measurements

“…Upon subsequent unloading, the residual levels decrease and are very close to those of scan 002. Damage growth did not yet occur, or if it had, it remained very low and at a scale lower than the scan resolution [ 33 ]. The significant increase in the correlation residuals compared to previous acquisitions is visible for scan 005.…”

Characterization of glass fiber reinforced polymer via Digital Volume Correlation: Investigation of notch sensitivity

“…This result indicated successfully converged correlations (the hypothesis of continuity of the displacement field was satisfied). Hence, damage growth did not yet occur, or if it had, it remained very low and at a scale lower than the scan resolution [28]. The subsequent unloading yielded homogeneous fields (Fig.…”