A laser system for high accuracy measurement of small apertures in mechanical parts

A simple, high accuracy small gap measurement system for rough industrial environments was designed and constructed. The system could detect apertures as small as 60µm with less than 6µm error in metallic parts with finite (cm range) depth. The principle is based in the transient analysis of transmitted laser intensity which is focused and swept along the region of the gap. The system is composed of a low power visible laser (semiconductor or He-Ne), focusing system, rotating mirror scanner, detection optics and amplifier, control unit for signal processing, speed control and data delivery to the process control unit.