Phase Flicker Optimisation in Digital Liquid Crystal on Silicon Devices

Phase flickers in the digital liquid crystal on silicon (LCOS) devices employing the pulse width modulation (PWM) driving scheme have a detrimental effect on the optical performances, especially in the non-display applications. This paper investigated the relationship between the PWM waveform and the corresponding phase flicker in digital LCOS devices. It has been identified that the magnitude of the phase flicker depends on the pulse patterns in the driving waveform as well as the dynamic response of the liquid crystal molecules at different tilting angles. A simple but generic method has been developed based on these findings, which is able to accurately predict the temporal phase response of the liquid crystal to any PWM waveforms. This method is further used for rapid identifications of low-flicker PWM waveforms, without the need for increasing the complexity of the driving circuitry. The peak-to-peak phase flicker in the LCOS device under our investigation has been reduced by >80% from <0.16pi to <0.03pi when operating at 30 ℃.