科研进展|液晶微偏振阵列为偏振相机的实现提供了新方法

Micropolarizer array is the core component of division of focal plane (DoFP) polarimeter. At present, the metal-wire-grid micropolarizer array has been commercialized in polarization cameras. Liquid crystal micropolarizer (LCMP) array can be designed to achieve a high extinction ratio and cover wider band. Therefore, it has great potential to develop a DoFP and achieve real-time polarization imaging.

 

In a study published in Optics Express, a research group led by Prof. MU Quanquan from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a 4-domain twisted LCMP array for visible linear polarization imaging.

 

The proposed LCMP array consisted of a pixelated twisted liquid crystal (LC) layer and a uniform linear polarizer. Based on the polarization rotation principle of twist nematic LC, the twist angles were designed to be ± 22.5° and ± 67.5°. A large birefringent LC material with independent intellectual property rights of the group was adopted to obtain the optimized polarization efficiency.

 

This LCMP array was fabricated using a digital micromirror device (DMD) lithography system, which effectively reduce the requirement of processing precision and simplify the processing procedure.

 

In order to verify the effectiveness of LCMP, a modular DoFP system prototype based on the LCMP was built for polarization imaging experiments. The results of experiments indicated that the LCMP has good uniformity and optical performance, which could meet the requirement of linear polarization imaging. LCMP also has the potential to be integrated onto an image sensor to develop a high-resolution, compact and cost-effective polarization camera.

 

Figure 1. Schematic diagram of a superpixel in the LCMP array (Image by ZHANG)