Optical device.

摘要

An optical device comprising a transparent plate (6) having planar first reflecting surface (6-a) and second reflecting surface (6-b), a reflector (8) and a screen (9) for forming interference fringes thereon. When a beam (5) is incident on the transparent plate (6), a portion (5-a) of the beam is reflected from the first reflecting surface (6-a), while the other portion (5-d) of the beam (5) enters the interior of the plate (6) and is reflected at the second reflecting surface (6-b). The beam (5-a) reflected from the frist reflecting surface and further reflected from the reflector (8)and the beam (5-d) reflected at the second reflecting surface (6-b) are superposed on the screen (9) to produce interference fringes. The period of the interference fringes is easily variable by rotating the reflector (8) and the screen (9) around the line of their intersection.