The microscopic examination of a planar sample in an oblique manner is proved to be feasible, indeed easy, using in conjunction with a microscope a simple attachment consisting of a unity magnification system and a diffraction grating. The illumination must be mono-chromatic. The unity magnification system focuses the sample onto the grating. The grating is chosen such that the first diffracted order corresponding to the incidence used in the arrangement is perpendicular to the grating. The grating is observed with the microscope in the conventional manner. The principle, properties, capabilities and limitations of this novel and versatile optical arrangement are explained and reviewed.
Jean Claude Chastang,
"Oblique Viewing Attachment For Microscope", Proc. SPIE 0399, Optical System Design, Analysis, and Production, (26 October 1983); doi: 10.1117/12.935437; https://doi.org/10.1117/12.935437