The curvature of the substrates is determined by the custom-built setup (Fig. A). Translation of the substrate by a distance Δd causes displacement of the laser beam on the CCD camera by a distance ΔD The curvature of the samples is determined as:
κ = 1/ROC = 1/L * ΔD/Δd
We measure the location of the reflected laser beam spot on camera [pixels] as function of translation stage step [steps].
The setup of measuring curvature of surfaces. The step size of the step motor traslating the sample is 2μm; the size of the CCD pixel is 7.4 μm; the sample-camera distance is L= 3.52 m. The estimated accuracy in determination of curvature is 0.01 m-1.