Zeng Zhen, Li Zexiao, Fang Fengzhou, Zhang Xiaodong
State Key Laboratory of Precision Measuring Technology & Instruments, Laboratory of Micro/Nano Manufacturing Technology, Tianjin University, Tianjin 300072, China.
Sensors (Basel). 2021 Feb 1;21(3):967. doi: 10.3390/s21030967.
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.
相位补偿是使用空间光调制器（SLM）的光学测量系统的关键步骤。SLM产生的波前畸变主要是由SLM物理结构的相位调制非线性和不均匀性以及环境条件引起的。本研究阐述了一种使用泰曼-格林干涉仪对硅基液晶空间光调制器（LCoS-SLM）进行相位调制特性校准和补偿的方法。提出了一种使用两组相位图序列的方法，以在像素级别校准LCoS-SLM整个孔径上的不均匀特性。计算相位补偿矩阵以校正LCoS-SLM的实际相位调制，并确保能够实现设计的波前。与先前已知的补偿方法相比，所提出的方法可以获得LCoS-SLM上每个像素的相位调制特性曲线，而不是整个LCoS-SLM孔径上对应于块阵列的单查找表（LUT）曲线或多LUT曲线。实验结果表明，相位补偿精度在波前方面可达到峰谷值0.061λ，并且该方法可应用于生成用于精确光学性能的自由曲面波前。
