An open-source, accurate, and iterative calibration method for liquid-crystal-based spatial light modulators

An iterative method for accurately measuring and calibrating liquid crystal-based spatial light modulators (SLMs) through Michelson interferometry is described here. In this framework, staggered fringes were formed by transversing the phase value displayed by half of the SLM from 0 to 2π while keeping the phase value displayed by the rest half to 0. Advanced digital signal processing was employed to extract phase values from measured staggered fringes, and the look-up-table values inherent in the SLM were updated accordingly. In practice, going through this phase measurement only once cannot always guarantee a satisfactory performance, possibly due to insufficient sampling during measurements and inaccurate interpolation during data processing. We show in this work that iteratively performing the above procedure several times can significantly reduce the phase differences between the measured phases and the desired ones. Experimentally, we validated the performance by calibrating two SLMs with different models and initial settings. We empirically found that the phase error, defined as the root-mean-square difference between the measured phase values and the desired ones, can be reduced to 0.01–0.02π within only three rounds of iterations. We anticipate that this iterative calibration method can be very helpful to SLMs-oriented applications.