Research On Defects Detection In Gluing Glass Using Photothermal Radiometry

Lightweight mirror is widely used in space telescope in the future. In the bondingprocess of lightweight mirror, various gluing defects such as flaws, delamination anddisbondings will come into being when cementing optical component. These defects inproducts will decrease the effective contact area significantly which have bad influenceto processing availability and surface reliability of glass. It will affect imaging quality ofsystem.In this paper, the research of bonding defects detection is explored. SeveralNon-destructive Test methods such as ultrasonic C-scan and visible light imaging areeffective in inspection of it at present, but both of them are limited by detectioncondition. Specimen need be put in coupling liquid when using ultrasonic C-scan. Theglue is demanded to transmit visible light when using visible light imaging. In this paper,on the basis of detection demands, photothermal radiometry is used to detect defects ingluing glass for the first time with the basic idea that glass-layer is look as a windowand glue-layer is heat source. Light is modulated to transmit glass-layer and heatglue-layer. By monitoring the temperature variation of glue-layer in time domain usinginfrared thermal detector, the defects can be discovered. Principle of the detectingmethod is analyzed. Math model of detecting process is created. The softwareMATLAB and ANSYS are respectively used to analyse the affection factor of result andfinite element analysis. And then, experiment is finished to prove the feasibility thatusing photothermal radiometry to detect defects in glue glass. At the same time, PTRcan be also used to detect bubbles inside of glass material. As detecting defects in glassgluing is at the exploring period, especially intensity and uniformity of infrared lightsource, accuracy of detector is required strictly, researches of quantitative analysis andengineering applicability are also need to improve.