Shape Inspection System for Variable-Luminance Steel Plates with Real-Time Adaptation Capabilities to Luminance Variations

Abstract This work presents an automated shape inspection system for two-dimensional plates with variable luminance. The system, installed in the rolling mill of a steel factory, captures linear images of plates at high temperatures (700–1200°C) while they are moving on a roll path. The main objective of the system is to capture and characterize the shapes of the heads and tails of the plates, in order to optimize the parameters of the rolling mill, and so to minimize wastage. To date, most of the research work done on illumination has focused on obtaining optimal illumination for the inspected objects. This work, however, deals with the particular case of objects that radiate their own light. This system automatically adapts itself to different levels of luminance using a mechanism that calculates the proper exposure time to acquire each image. The mechanism combines a feedforward control with an adaptive feedback control loop for the exposure time.