Possible configurations of the ingot prism. Column (1): Number of desirable faces. Columns (2)–(3): LGS sections and corresponding pupils. Note: the arrangement of the pupils is purely conceptual, the real position will depend on the considered optic implementation. Column (4): possible design of the prism. Column (5): signals that can be measured by considering the upper, medium and lower regions. Column (6): notes according to Fig. 7.