A Smartphone-Based Laser Measuring System for Gap and Flush Assessment in Car Body

This article presents a portable smartphone-based laser measurement system (SLM) for measuring gaps and flushes on a car body. The system is designed to replace conventional gauges that are used by human operators. The developed device consists of a smartphone and an off-The-shelf laser-line projector held together by a three-dimensional-printed structure. It captures images of a laser line scattered on target surfaces, identifies the extreme points on the laser profiles, and obtains gap and flush measurements with minimal uncertainty. Since the smartphone is used as the operational unit, the measurement data can be stored and allows the capability for data transfer with other storage locations. Experiments were performed on the specimens and real cars to validate the application of the developed system. The measurement uncertainty on a real car was reported as \pm 0.201 mm for gap and \pm 0.154 mm for flush.