Abstract
This paper describes optical measuring method to obtain inner radius of transparent capillary. There are two modes as to optical path which beam refracts and transmits in the capillary. These modes are called tangential mode and one order reflection mode. The inner radius of the capillary can be obtained by measuring transmission angle and transmission distance in each mode. The angle and distance are measured automatically by using rotary table and X table assembled stepping motor controllable by a microcomputer. The optical intensity of transmitted beam is transformed into voltage by a phototransistor and the determination of the angle and distance is performed by detecting maximum voltage. In spite of optical measurement, it is not necessary in this method to measure the index of refraction of capillary material. From experimental results the accuracy of new measuring method is ±1/500 mm.
