Phase calibration of spatial light modulators using self-generated phase-discontinuity

In this paper, we introduce a new method for precise determination of the calibration function of liquid crystal spatial light modulators (LC-SLMs). The proposed method shares the advantages of commonly used methods, interferometric and diffraction-based methods, and is free of their disadvantages. The method proposed here is based on the evaluation of Fresnel diffraction of light from a phase-discontinuity pattern loaded into the SLM device. In one version, the phase step pattern consists of two parts, one remains constant at zero, while the other changes with steps of 5 from 0 to 255 gray levels, for each measurement. By fitting the experimental intensity distribution measured in this configuration on the corresponding theoretical intensity distribution, complete phase calibration can be obtained. We also propose a second version, employing a phase wedge pattern, allowing the phase calibration curve of the SLM to be determined by just a single frame measurement which is a great asset.