Auto-synchronized laser scanning range sensor for thermoplastic pavement marking material thickness measurement

摘要

Pavement marking materials provide delineation on highways around the world. The condition of the marking materials is very important for the driver's safety as well as the comfort and the driving expenses. Currently thermoplastic pavement marking materials (TPMM) are widely used in states. Measuring the thickness of TPMM on pavement is an essential index to monitor the contractors, calculate durability of marking materials, and provide better information for the pavement marking evaluation. In recent years to measure the thickness of TPMM, a procedure involving pre-embedded plates sprayed with the marking materials has been widely accepted. This method is labor intensive, and cannot obtain a continuous-thickness profile. Therefore there are demands to develop a high-speed automatic measuring system for determining the thickness and uniformity of marking materials. In this paper, a laser range sensor based on auto-synchronized laser scanning is proposed for the thermoplastic pavement marking material thickness measurement. Compare to classical triangulation method, this approach doesn't scarify the system resolution for large field of view and it is more suitable for highway speed measurement. To achieve high speed measurement, PSD (Position Sensitive Detector) is used in the prototype system instead of CCD (Charge Couple Device) in traditional auto-synchronized system. The standoff distance and transverse scan range of the prototype system both are 1 foot. The lab test results show that the prototype system can measure the thermoplastic type thickness with error in 5mil at laser scanning rate up to 50Hz.