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.
Highlights
With the wide spread of flat panel displays (FPDs), people can choose to read contents of differently-sized fonts based on their preference and visual ability
We propose the use of a tuneable liquid crystal micro-lens (LCML) array to improve imaging contrast of the thin film photo-transistor (TFPT) flat panel imager
The LCML array used in this work consists of a proprietary nematic LC layer sandwiched between two display glass substrates, which were made in a cleanroom environment
Summary
With the wide spread of flat panel displays (FPDs), people can choose to read contents of differently-sized fonts based on their preference and visual ability. In order for elderly and visually impaired people to read print on papers such as books, newspapers, and product tags/labels more efficiently, electronic magnifying viewers or video magnifiers have been developed [4]. They are better than conventional optical magnifiers because they can adjust brightness and contrast electronically to make the contents easier to read as well as have an option to choose from many levels of magnifications (e.g., from 1.5× to 50×) [5]. Users have to move the viewer along the contents, and it is easy to lose track of where they are on the paper [9,10]
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