Question

From which part the light column is divided into beams in grazing incident technique?

(a) At the hypotenuse of the system’s precision prism

(b) At base of the system’s precision prism

(c) After reflecting from the test surface

(d) At perpendicular of the system’s precision prism

This question was addressed to me in a job interview.

This intriguing question comes from Grazing Incident Technique to Evaluate Surface Flatness topic in chapter Machine Vision Systems of Engineering Metrology

Answer 1

The correct choice is (a) At the hypotenuse of the system’s precision prism

Explanation: At the hypotenuse of the precision prism of the system, the light column is divided into two beams i) the reference and ii) test beam. When these beams recombine, they interfere with one another and create a series of light and dark bands or an interference pattern.