An optical-based system (100, 200, 300, 500) configured to validate an orientation of an internal facet of a sample relative to an external, flat first surface of the sample, wherein the sample comprises a first part and a second part, between which the internal facet extends, wherein the first part is positioned between an external second surface of the sample and the internal facet, the system comprising: a light guiding arrangement, LGA (102, 202, 302, 502) configured to redirect light, which is incident on the LGA (102, 202, 302, 502) in a direction perpendicular to an external and flat first surface of the sample, into or onto the sample, such that light, transmitted thereby into the sample, impinges on an internal facet of the sample nominally normally to the internal facet; an illumination and collection arrangement, ICA (104, 204, 304, 504) comprising: a light generation assembly configured to ( a) project a first incident light beam, LB, on the first surface, so as to generate a first returned LB by reflection off the first surface, and (b) project a second incident LB on the LGA (102, 202, 302, 502), in parallel to the first incident LB, so as generate a second returned LB, by redirection by the LGA (102, 202, 302, 502) of the second incident LB into or onto the sample, reflection thereof off the internal facet, and inverse redirection by the LGA (102, 202, 302, 502); wherein the LGA (102, 202, 302, 502) is configured to redirect the second incident LB into or onto the first part of the sample via the second surface; and at least one sensor (114, 514), configured to measure a first angular deviation of the second returned LB relative to the first returned LB, and/or an eyepiece assembly configured to enable manually measuring the first angular deviation; wherein the measured first angular deviation is indicative of an actual inclination angle of the internal facet relative to the first surface. a light guiding arrangement, LGA (102, 202, 302, 502) configured to redirect light, which is incident on the LGA (102, 202, 302, 502) in a direction perpendicular to an external and flat first surface of the sample, into or onto the sample, such that light, transmitted thereby into the sample, impinges on an internal facet of the sample nominally normally to the internal facet; an illumination and collection arrangement, ICA (104, 204, 304, 504) comprising: a light generation assembly configured to ( a) project a first incident light beam, LB, on the first surface, so as to generate a first returned LB by reflection off the first surface, and (b) project a second incident LB on the LGA (102, 202, 302, 502), in parallel to the first incident LB, so as generate a second returned LB, by redirection by the LGA (102, 202, 302, 502) of the second incident LB into or onto the sample, reflection thereof off the internal facet, and inverse redirection by the LGA (102, 202, 302, 502); wherein the LGA (102, 202, 302, 502) is configured to redirect the second incident LB into or onto the first part of the sample via the second surface; and at least one sensor (114, 514), configured to measure a first angular deviation of the second returned LB relative to the first returned LB, and/or an eyepiece assembly configured to enable manually measuring the first angular deviation; a light generation assembly configured to ( a) project a first incident light beam, LB, on the first surface, so as to generate a first returned LB by reflection off the first surface, and (b) project a second incident LB on the LGA (102, 202, 302, 502), in parallel to the first incident LB, so as generate a second returned LB, by redirection by the LGA (102, 202, 302, 502) of the second incident LB into or onto the sample, reflection thereof off the internal facet, and inverse redirection by the LGA (102, 202, 302, 502); wherein the LGA (102, 202, 302, 502) is configured to redirect the second incident LB into or onto the first part of the sample via the second surface; and at least one sensor (114, 514), configured to measure a first angular deviation of the second returned LB relative to the first returned LB, and/or an eyepiece assembly configured to enable manually measuring the first angular deviation;