| dc.description |
This paper describes an apparatus for intercomparing two or more length gauges, of nominally equal length, by interference methods. It consists of a tilting lever, resting on three ball feet, two of which are supported from the base of the apparatus, whilst the third rests in turn on the various gauges to be compared. The lever carries at the top a polished flat steel surface, over which an optical proof plane can be adjusted to give the desired pitch and direction to the interference fringes which appear when the apparatus is suitably illuminated with monochromatic light. A simple optical scheme is also described. The comparison of the gauges is effected by placing them in turn under the third foot of the tilting lever, and counting the number of fringes, in whole numbers and tenths, which fall within a given space. The difference between the gauges in inches is then K((n<sub>1</sub> - n<sub>2</sub>)/2)λ, where n<sub>1</sub> and n<sub>2</sub> are the number of fringes produced by each gauge in turn, and λ is the wave-length (in inches) of the radiation used, and K is a constant depending upon the magnification of the lever arrangement. |
