Method and apparatus for inspection of panel embedded dies using combined thermal and optical imaging

A system comprising:

• a thermal subsystem comprising:
• a first laser light source configured to emit laser light;
• a first focusing lens configured to direct the laser light from the first laser light source onto a workpiece;
• and
• a thermal camera configured to capture a thermal image of the workpiece;
• an optical subsystem comprising:
• at least one light source configured to emit light with at least one illumination modality;
• a light focusing lens configured to direct the light from the at least one light source onto the workpiece;
• and
• a detector configured to capture at least one image of the workpiece;
• and
• a processor in electronic communication with the thermal subsystem and the optical subsystem, wherein the processor is configured to:
• compare the at least one image received from the detector to at least one reference image to for registration of the workpiece or to determine presence of a surface defect on the workpiece;
• and
• determine presence of a bulk defect in the workpiece based on the thermal image, wherein the processor is configured to determine the presence of the bulk defect in the workpiece based on the thermal image by:
• obtaining an intensity of each pixel of the thermal image along an edge of the workpiece;
• deriving a gradient map representing a spatial derivative of a temperature profile along the edge of the workpiece using the intensity of each pixel of the thermal image;
• determining that the bulk defect in the workpiece exists where there is a peak in the gradient map;
• and
• determining that no bulk defect exists in the workpiece where there is no peak in the gradient map.