An FPGA-Based Laser Virtual Scale Method for Structural Crack Measurement

Abstract

Real-time systems for measuring structural cracks are of great significance due to their computational and cost efficacy, inherent hazards, and detection discrepancies associated with the manual visual assessment of structures. The precision and effectiveness of image measurement approaches increased their applications in vast regions. This article proposes a field-programmable gate array (FPGA)-based laser virtual scale algorithm for noncontact real-time measurement of structural crack images. The device first sends two parallel beams and then applies image processing techniques, including de-noising with median and morphological filtering, as well as Sobel-operator-based edge extraction, to process and localize the light spots. Afterwards, it acquires the scale of the pixel distance to the physical distance and then derives the actual size of the crack. By processing and positioning, the FPGA acquires the scale of the pixel distance to the physical space and then derives the actual size of the crack. The experimental study on crack measurements demonstrates that the proposed technique has precise and reliable results. The error rate is approximately 2.47%, sufficient to meet measurement accuracy criteria. Moreover, experimental results suggest that the processing time for one frame using an FPGA is about 54 ms, and that the hardware acceleration provided using an FPGA is approximately 120 times that of a PC, allowing for real-time operation. The proposed method is a simple and computationally efficient tool with better efficacy for noncontact measurements.