When laser micro welding is applied to assemble the optoelectronic packages, rapid cooling of the welded region and the associated material shrinkage often cause micro thermal distortion between the weld parts. If the thermal distortion induced by the joining process is even a few micrometers, up to 50% loss in coupled power of the package laser will be incurred, resulting in its performance degradation. Therefore, it is important to measure the thermal distortion between the welded joints.
In this study, the recording of ESPI(Electronic Speckle Pattern Interferometry), arranged for sensitive measurement out-of-plane distortion, is combined with laser speckle correlation to measure all three components of the distortion. In measuring the distortion of optoelectronic packages, there is the saturation of the image in the centerline of the tube. Tilting optoelectronic packages and increasing the shutter speed of CCD camera are found to be effective for reducing the image saturation.
A modified correlation technique is used to calculate correlation fringe patterns of optoelectronic packages. Although more calculation are required than in standard image differencing routines, an advantage of this method is that more clear fringe patterns are obtained with nonuniform illumination over the surface than in standard image differencing routines and correlation fringe technique.
