Coded Illumination Under Quantized Luminosity for Visual Inspection

Abstract

This paper addresses the optimization of illumination and camera imaging conditions in imaging systems equipped with multi-channel illumination for visual inspection. While previous studies have primarily focused on HDR imaging, in practical settings HDR acquisition is time-consuming and typically performed using a single fixed exposure time. To enable the practical application of coded illumination for visual inspection, we extend the method to jointly optimize camera exposure time along with illumination conditions. We propose a unified framework that optimizes both texture and brightness based on BTF, leveraging the full expressive power of the imaging device under the common hardware constraint that illumination luminance is quantized. Furthermore, we demonstrate that the global optimum of Fisher’s LDA, subject to non-negative light intensity constraints, can be computed using SDP, and this solution effectively enhances foreground contrast. Experimental results show strong agreement between simulated and real images in an actual visual inspection hardware environment, thereby validating the feasibility of illumination condition optimization using a digital twin approach.