Li Kun, Chu Daping, Chu Jiaqi, Kitajima Shuhei, Matsuda Tokiyoshi, Kimura Mutsu
Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
Department of Electronics and Informatics, Ryukoku University, Seta, Otsu 520-2194, Japan.
Micromachines (Basel). 2017 Jun 26;8(7):205. doi: 10.3390/mi8070205.
We propose and demonstrate the concept of using a tuneable liquid crystal micro-lens (LCML) array to improve the image contrast of a pixelated thin film photo-transistor (TFPT) flat panel imager. Such a device can be used to image contents on paper-based media and display a magnified version on a flat panel display for elderly or visually impaired people. Practical aspects including device physical geometry, object scattering profile, LC material, and focusing effect of LCML on an object are considered during the design process with the support of ZEMAX simulations. An optimised effective focal length (EFL) has been calculated for the designed LCML to best relay the objects or contents on a paper to the TFPT pixel plane. The designed LCML devices are fabricated with the optimised EFL, and they have good phase depth profiles which are close to a spherical lens profile. Preliminary test results show that the combination of a TFPT imager with an LCML array can make the image contrast more than two times better than that using the TFPT imager alone. The tuneable EFL of the developed LCMLs are useful in the situation where the LCML is not in direct contact with the imaged object.
我们提出并演示了使用可调谐液晶微透镜（LCML）阵列来提高像素化薄膜光电晶体管（TFPT）平板成像器图像对比度的概念。这种设备可用于对纸质介质上的内容进行成像，并在平板显示器上为老年人或视力障碍者显示放大版本。在设计过程中，借助ZEMAX模拟，考虑了包括器件物理几何形状、物体散射轮廓、LC材料以及LCML对物体的聚焦效果等实际问题。已为设计的LCML计算出优化的有效焦距（EFL），以便将纸张上的物体或内容最佳地中继到TFPT像素平面。所设计的LCML器件采用优化的EFL制造，并且具有接近球面透镜轮廓的良好相位深度分布。初步测试结果表明，TFPT成像器与LCML阵列的组合可使图像对比度比仅使用TFPT成像器时提高两倍以上。所开发的LCML的可调谐EFL在LCML不与成像物体直接接触的情况下很有用。
