Reference Modulation for High-Quality Scan Images of 2-D Laser Scanner Systems

For laser scanner systems, the most critical issue for high-quality images is the linearity of the slow axis. The laser scanner systems have various disturbances and uncertainties, such as manufacturing tolerances, structure vibrations, and parameter uncertainties. Further, there are vertical and horizontal resonance modes that hinder controller design. In this letter, we propose a reference modulation technique to enhance the vertical angle linearity of the slow axis for two-dimensional laser scanner systems. First, the laser scanner system is mathematically modeled in the state-space form. Then, the reference modulation is designed to boost the loop gain over the desired frequency range. The reference modulation can guarantee high-quality scan images by redesigning the desired reference based on the output feedback. The current tracking controller was then implemented with virtual references for the states. We investigated its tracking performance via sensitivity function analysis against the disturbances. Experiments were performed to evaluate the effectiveness of the proposed method using four different laser scanners. We confirmed that the proposed method achieved up to 48% improvement in the angle tracking error from the experimental results.