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Micromachines 2017, 8(7), 205; doi:10.3390/mi8070205

Tuneable Liquid Crystal Micro-Lens Array for Image Contrast Enhancement in a Pixelated Thin Film Photo-Transistor Flat Panel Imager

1
Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK
2
Department of Electronics and Informatics, Ryukoku University, Seta, Otsu 520-2194, Japan
*
Author to whom correspondence should be addressed.
Received: 12 June 2017 / Revised: 20 June 2017 / Accepted: 23 June 2017 / Published: 26 June 2017
(This article belongs to the Collection Laser Micromachining and Microfabrication)
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Abstract

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. View Full-Text
Keywords: liquid crystal micro-lens; optical relay; thin film photo-transistor; image contrast liquid crystal micro-lens; optical relay; thin film photo-transistor; image contrast
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Li, K.; Chu, D.; Chu, J.; Kitajima, S.; Matsuda, T.; Kimura, M. Tuneable Liquid Crystal Micro-Lens Array for Image Contrast Enhancement in a Pixelated Thin Film Photo-Transistor Flat Panel Imager. Micromachines 2017, 8, 205.

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