GB600234A - Improvements in or relating to interferometric gauges for linear dimensions - Google Patents

Abstract

600,234. Interferometers. BENDIX AVIATION CORPORATION. Nov. 28, 1945, No. 32197. Convention date, Dec. 16, 1944. [Class 97 (i)] [Also in Group XIX] An interferometric gauge, more particularly for internal gauging, comprises two optical flats 19, 21, to which are attached, respectively, calliper arms 76, 77, and a viewing system so arranged that the light reflected from the adjacent surfaces of the optical flats may be viewed in the eyepiece. The lower flat 21 is mounted in a holder 22 hinged to a base 17 by flexible metal plates 23, 24 clamped to the base by blocks 25, 26 and screws (Fig. 4). The upper flat 19 in a holder 44 is similarly hinged to a yoke member 41 clamped to the base 17. The yoke may be adjusted vertically by bolts 61, 62. A levelling optical flat 69 is adjustably mounted in the base 17 below the gauging flat 21. The upper and lower surfaces of the lower gauge flat 21 are formed at a small angle to allow interference fringes between the gauging flats and the levelling flat 69 and lower gauge flat 21 to be viewed separately by a slight adjustment of a support 10 for the viewing system. The calliper arms 76, 77 are rigidly attached to the carriers for the gauge flats, their free ends being provided with jewel points. The arm 77 is formed integral with the carrier 22 and is provided with a longitudinal slot in which the arm 76 is movable. The arm 76 is provided with a dovetail extension 83 held in position by cap screws 84 which bear against the carrier 44. In operation a plane table 18 is provided with a standard gauge fixture 100 with platform 104 on which rest two optical flats 105, 106 separated by standard blocks of the required size. The gauge 116 which is to be measured is placed in a suitable holder 117 seated on a mounting surface 101 which may be-levelled by screws 133, 134, 135. The holder is provided with eccentric buttons 125, 126, 127 rotation nf which moves the holder 117 to locate the gauge ring 116 with respect to the gauge arms. The difference in the number of fringes compared with the standard gives a measure of the diameter. A light source 1, comprising a gaseous tube connected to a transformer 2, is mounted in the end of a cylinder 11 adjustably supported by a bracket 12 carried by a crossbar 13. A lens 14 and inclined mirror 15 are arranged at the opposite end of the cylinder. The whole instrument may be housed in an airconditioned and temperature-controlled chamber of the type described in Specification 598,282.