Analysis and Modeling of Surface Waviness Inspection with Light Reflection, Part 3: Light Intensity Distribution Method

Abstract

The light intensity distribution method for inspecting a reflective surface using a diffusing or retroreflective screen has been studied. Analytical derivations show that the angular light intensity in the screen projection is related to the surface curvature. Numerical modeling with light tracing and intensity accumulation is developed to simulate the D-Sight image formed by double reflection off a part surface with a retroreflective screen. The cone angle of a retroreflective screen is characterized experimentally. The numerical modeling is validated with an analytical solution and then tested by comparing the predicted with the photographed D-Sight images of a profiled SMC (sheet molding compound) panel. The characteristics of double reflection and the effects of eye-to-light distance, eye position relative to the light, angular dependence of intensity distribution inside a retroreflected cone, and surface waviness orientation on the image are investigated. The images of typical surface features are predicted.