An inspection technology of inner surface of the fine hole based on machine vision

TL;DR

This paper presents a machine vision-based inspection system for assessing the inner surface quality of fine holes, employing specialized optical setup and error compensation to achieve precise measurements.

Contribution

It introduces a novel optical measurement system with a flexible light array and error analysis for inner surface inspection of fine holes.

Findings

Maximum measurement error standard deviation around 10μm

Minimum measurable hole diameter is 4mm

Depth measurement capability up to 47mm

Abstract

Fine holes are an important structural component of industrial components, and their inner surface quality is closely related to their function.In order to detect the quality of the inner surface of the fine hole,a special optical measurement system was investigated in this paper. A sight pipe is employed to guide the external illumination light into the fine hole and output the relevant images simultaneously. A flexible light array is introduced to suit the narrow space, and the effective field of view is analyzed. Besides, the arc surface projection error and manufacturing assembly error of the device are analyzed, then compensated or ignored if small enough. In the test of prefabricated circular defects with the diameter {\phi}0.1mm, {\phi}0.2mm, 0.4mm distance distribution and the fissure defects with the width 0.3mm, the maximum measurement error standard deviation are all about 10{\mu}m. The minimum diameter of the measured fine hole is 4mm and the depth can reach 47mm.