Method and apparatus for scanning a test object

An apparatus for scanning a test object, comprising:

• a mechanical scanner;
• a probe mounted on the mechanical scanner;
• and
• a controller operably connected to the mechanical scanner and to the probe, the controller being configured to:
• control a scanning motion of the probe to obtain a plurality of measurements for a corresponding plurality of scanning points on a surface of a reference object;
• build a gain correction map including a plurality of gain values calculated as a function of the plurality of scanning points on the surface of a reference object;
• control a scanning motion of the probe to obtain a plurality of measurements for a corresponding plurality of scanning points on a surface of the test object;
• and
• normalize amplitudes of the plurality of measurements obtained for the plurality of scanning points on the surface of the test object using the gain values of the gain correction map.