Optical-based validation of orientations of internal facets

An optical-based method for validating an orientation of one or more internal facets of a sample relative to an external, flat first surface thereof, the method comprising:

• providing a sample comprising the external, flat first surface and an internal facet nominally inclined at a nominal inclination angle p relative to the first surface;
• providing a light guiding arrangement (LGA) configured to redirect light, which is incident on the LGA in a direction perpendicular to the first surface, into or onto the sample, such that light, transmitted thereby into the sample, impinges on the internal facet nominally normally to the internal facet;
• generating a first incident light beam (LB), directed at the first surface normally thereto, and a second incident LB, parallel to the first incident LB and directed at the LGA;
• obtaining a first returned LB by reflection of the first incident LB off the first surface;
• obtaining a second returned LB by redirection by the LGA of the second incident LB into or onto the sample, reflection thereof off the internal facet, and inverse redirection by the LGA;
• measuring a first angular deviation of the second returned LB relative to the first returned LB;
• and
• deducing an actual inclination angle p′ of the internal facet relative to the first surface, based at least on the measured first angular deviation.