Precision inspection of transparent component quality

Abstract

In this work, a method using transmission interferometry is proposed to detect surface defects on transparent materials. This technique is non-destructive and non-contact for the analysis of transparent and optical components whose surfaces vary from a few mm2 to larger sizes. The purpose of this method is to provide, a means as simple as possible to identify defects with low contrast, and in particular barely visible defects, and of differentiate between the defects. The constructed transmission system generates fringes by the superposition of two microscopic periodic structures. According to the method, the test structure deforms after passing through the object. The information about surface defects is obtained from the object analyzed, and superposed on reference structure similar to test structure. Then, fringes are collected with information transported in the variation of their form. It is possible to clearly identify microscopic and submicroscopic defects thanks to the implementation of high-resolution detection in the nanoscale. The magnifying properties of the technique, up to 1000 times, allow better observation of defects which facilitates the automation of measurements and controls. Therefore, the proposed method can be suitable for the detection of surface defects in transparent optical objects such as optical films, lenses, prisms.