Phase Compensation of the Non-Uniformity of the Liquid Crystal on Silicon Spatial Light Modulator at Pixel Level

Abstract

Phase compensation is a critical step for the optical measuring system using spatial light modulator (SLM). The wavefront distortion from SLM is mainly caused by the phase modulation non-linearity and non-uniformity of SLM’s physical structure and environmental conditions. A phase modulation characteristic calibration and compensation method for liquid crystal on silicon spatial light modulator (LCoS-SLM) with a Twyman-Green interferometer is illustrated in this study. A method using two sequences of phase maps is proposed to calibrate the non-uniformity character over the whole aperture of LCoS-SLM at pixel level. A phase compensation matrix is calculated to correct the actual phase modulation of the LCoS-SLM and ensure that the designed wavefront could be achieved. Compared with previously known compensation methods, the proposed method could obtain the phase modulation characteristic curve of each pixel on the LCoS-SLM, rather than a mono look-up table (LUT) curve or multi-LUT curves corresponding to an array of blocks over the whole aperture of the LCoS-SLM. The experiment results show that the phase compensation precision could reach a peak-valley value of 0.061λ in wavefront and this method can be applied in generating freeform wave front for precise optical performance.

Spatial Light Modulators and Their Applications in Polarization Holography

“…The modern SLM calibration techniques are typically based on Polarimetric methods accompanied by digital holography [45,46]. Moreover, the consolidation of digital holography with polarimetry has paved the convenient approach to SLM calibration.…”

57.2: Error Analysis in LCoS Phase Uniformity Measurement with Classical Polarimetric Method for Holographic Display Applications

“…Another outcome to notice is that the effect of back reflection is mainly due to the changing interference caused by overmodulation under different phase input, so it not only affects the classical polarimetric method discussed in this paper, but can also affect other LCoS phase measuring methods based on phase retrieving from normalized light intensity, including binary grating method [16] and some interference methods [3,4]. Figure 4.5 shows the measured phase result with binary grating method on the same LCoS panel, and similar ripple-shaped error pattern is also present in this result.…”

“…Multiple research groups [3,4,5] have presented interferometry methods to measure and calibrate the reflected wavefront from LCoS-SLMs, and such methods have become the first choice for measuring the LCoS phase uniformity whenever available. Figure 1.1 shows one of the possible optical setups for interferometry measurement of the LCoS wavefront, proposed by [4].…”

“…Multiple research groups [3,4,5] have presented interferometry methods to measure and calibrate the reflected wavefront from LCoS-SLMs, and such methods have become the first choice for measuring the LCoS phase uniformity whenever available. Figure 1.1 shows one of the possible optical setups for interferometry measurement of the LCoS wavefront, proposed by [4]. However, due to the nature of interferometry, these methods usually require a highly stable environment with minimal vibration and ambient light [6], which is not always available in every circumstance.…”

High Precision Optical Wavefront Generation Using Liquid Crystal Spatial Light Modulator (LC-SLM)

“…In practice, the methods of the latter category, interferometry-based methods, are more widely applied. In the latter category, typically a Michelson interferometer is used to capture the fringe pattern of the static aberration [32][33][34][35][36][37][38]. Furthermore, the fringe pattern can be demodulated to obtain the final true phase of aberration, by utilizing the phase-shift technology.…”