Development of a 3-dimensional precision measuring method by optical endoscope (Evaluation of measuring accuracy of inner wall based on quartz pipe surface)

Abstract

Newly developed 3D scanning optical endoscopic probe consists of φ1.5mm quartz pipe and 2 micro motors that run inside and conduct helical 3D scanning. This research looks into the possibility of accurately measuring the inner wall of extremely small diameter object by combining 3D scanning endoscopic optical probe and OCT (optical coherence tomography). Conventionally, precision measurement of such extreme inner diameter size was not possible due to influence of what is called “fluctuation of light” and “mechanical run-out of the measuring instrument itself” in axial and radial direction. In the new method, the inner wall of quartz pipe is measured in advance by calibration work, and the inner wall of the object is measured based on the quartz pipe. Applying this method, we succeeded in measuring with standard variation 0.07μｍ(σ) repeatedly. This new method also features auto-correction of the incline angle between the optical probe and the measuring object by computing, which prevents setting error and variation.