Determination of the Melting Point of Solids by the Imaging Acousto-Optical Filter

The aim of this report is to demonstrate that the use of the laser heating (LH) system combined with an imaging tandem acousto-optical tunable filter (TAOTF) allows determination of the melting point of a solid under infrared laser (IR, 1070 nm) heating and observation of the development of melting. Statistical analysis of a selected area of speckle interference patterns on the surface of a solid specimen (tungsten plate) under laser heating was applied to detect the beginning of melting. The advantage of this method is that the LH-TAOTF system provides two dimensional (2D) temperature distribution under LH of a specimen with a spatial resolution of 2 mu m. The information of the temperature distribution combined with the statistical processing of speckle enables us to determine the area and the temperature where melting begins.