Abstract
This paper describes a non-contact method for measuring the flatness of a mirror or a mirror-like surface by reflection of light beams from a group of line light sources arranged horizontally on a plane meeting at an angle of 45° with the horizontal plane. The light beams from these light sources are projected onto, in the first place, a liquid surface at rest, and in the next place, a mirror surface to be measured. With each projection the reflecting light beams are focused into an image on a screen separately provided, and by comparing both meanderings of the images of line light sources on the screen, the authors obtained the flatness of the mirror, the deviation between the mirror and the ideal geometrical plane. In tis paper, the authors propose the measuring principle, measuring errors and experimental results of the above method, and make it clear that the flatness of the mirror surface can be obtained mechanically at an arbitrary magnifying ratio by measuring only the meanderings of the images of light sources.
