A simple technique for measuring thickness distribution of transparent plates from a single image by using the sampling moiré method

A simple measurement technique for the thickness distribution of transparent plates is proposed by using the sampling moiré method. The thickness distribution is automatically analyzed by measuring the phase difference of the moiré fringe obtained from a single image, consistent with light refraction. The relationship between the actual thickness and phase difference of the moiré fringe is calibrated by using glass plates of known thicknesses. The thickness measured by the present method was found to be in agreement with measurements using a digital micrometer. In our experiment, the average error in glass plate thickness was 1.9% over a 3.5 mm measurement range. Experimental results indicate that the present method can be useful for nondestructive measurements of the thickness distribution of various transparent plates