Abstract: Mechanical stress applied to a crystal (10) by a procedure for forming a bond (13) between an electrical connector (12) and a metallized surface (11) of the crystal (10) is measured to obtain a quantitative indication of the quality of the bond (13). A beam of optical radiation generated by an illuminator (21) is divided by a first beamsplitter (22) into a first component and a second component. The power of the first component is measured by a first detector (23). The second component is circularly polarized by a circular polarizer (24), collimated by an imaging lens (25), and directed as an incident beam along an optical path through the crystal (10) to the metallized surface (11) in the vicinity of the bond (13). The metallized surface (11) reflects the incident beam back along the same optical path as a return beam.