The variable slit is the key module of the lithographic lighting system, which determines the performance of the exposure system. Its high‐precision field of view control puts forward strict requirements for dynamic response. To solve the problems caused by dynamic lag error and complex control, a prospective control technology based on the hidden Markov model (HMM) is proposed to predict the future state of the system, compensate the dynamic error, and improve the servo precision. The error transmission path is analyzed, and the upper limit of the theoretical error is determined by establishing the variable slit motion model. The HMM is used to deal with the uncertainty and time characteristics of the system, and the dynamic error can be compensated prospectively. The experiment shows that the maximum error of the traditional method is 8 um when the speed is 50 mm/s. However, after utilizing HMM, the error was reduced to ±2.5 um, significantly improving the servo accuracy of the system and demonstrating the potential for optimizing motion control performance.
Tu et al. (2026) studied this question.