Large range nano autofocus method based on differential centroid technique

•A large range nano autofocus method based on differential centroid technique is proposed for lithography systems.•A complete theoretical model was established and the linear representation of the differential signal was obtained.•The influences of system parameters on the curves were simulated, and the optimal system parameters were selected.•Experiments proved that the coarse autofocus range of the system is 169.5 µm, the fine autofocus range is 22 µm.•Experiments proved that the sensitivity of the system is 25 nm and the magnitude of the noise does not exceed 7.5 nm.The stability and practicability of the method are proved, and it can be used in high-precision lithography systems.