Optimization of dynamic structured illumination for surface slope measurements

We present a fast and ambiguity-free method for slope measurement of reflective optical elements based on reflectometry. This novel reflectometric method applies triangulation to compute the slope based off projected patterns from an LCD screen, which are recorded by a camera. Accurate, ambiguity-free measurements can be obtained by displaying one pixel at a time on the screen and retrieving its unique image. This process is typically accelerated by scanning lines of pixels or encoding the information with phase using sinusoidal waves. Various classes of solutions exist, centroiding and phase-shifting being the most accepted, but their sensitivities vary with experimental conditions. This paper demonstrates solutions based on various parameters such as accuracy or efficiency. The results are presented in a decision matrix and merit function. Additionally, we propose a new class of solutions – Binary Square screens – in an attempt to address system limitations and compare current systems to our solutions using the decision matrix. Several test conditions are proposed along with the best suited solution.