Approaches For A Destructive Measurement Method Of Subsurface Damages

Abstract

In optical manufacturing, the depth of subsurface damages (SSD) depicts an important quality aspect of optical elements. Nowadays, the investigation methods of the damage zone are mostly destructive and allow a sampling of the substrates only. This leads to a lack of statistical reliability. In this paper, one aim is to develop an easy and cheap procedure to evaluate the probes. Therefore, a spherical polishing and chemical etching is introduced. By means of imaging processing software the acquired data is analysed, which eliminates the operator influence und increases the reproducibility. Applying binarizing and shape detection algorithms the SSD structures is detected and the number of pixels per structure is calculated. The percentage of SSD over the depth fit with an exponential curve displays a maximum depth as a single value. The development of a method to choose the best threshold value represents an approach to quantify the uncertainty of the resulting SSD-depth.