A multi-regions electrically tunable liquid crystal microlens array for extending the depth of field

Plenoptic cameras have received a wide range of research interest because it can record the 4D plenoptic function or radiance including the radiation power and ray direction. One of its important applications is digital refocusing, which can obtain 2D images focused at different depths. To achieve digital refocusing in a wide range, a large depth of field (DOF) is needed, but there are fundamental optical limitations to this. In this paper, we proposed a plenoptic camera with an extended DOF by integrating a main lens, a tunable multi-focus liquid-crystal microlens array (TMF-LCMLA), and a complementary metal oxide semiconductor (CMOS) sensor together. The TMF-LCMLA was fabricated by traditional photolithography and standard microelectronic techniques, and its optical characteristics including interference patterns, focal lengths, and point spread functions (PSFs) were experimentally analyzed. Experiments demonstrated that the proposed plenoptic camera has a wider range of digital refocusing compared to the plenoptic camera based on a conventional liquid-crystal microlens array (LCMLA) with only one corresponding focal length at a certain voltage, which is equivalent to the extension of DOF. In addition, it also has a 2D/3D switchable function, which is not available with conventional plenoptic cameras.

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Fabrication of a Liquid Crystal Microlens Array Film with Oligothiophene-Doped Polymerizable Liquid Crystals

Molecular Crystals and Liquid Crystals ◽

10.1080/15421400903054394 ◽

2009 ◽

Vol 511 (1) ◽

pp. 298/[1768]-308/[1778]

Author(s):

Motoi Kinoshita ◽

Tomohiro Kobayashi ◽

Atsushi Shishido ◽

Tomiki Ikeda

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Microlens Array

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Electrically Tunable-Focusing Liquid Crystal Microlens Array with Simple Electrode

Crystals ◽

10.3390/cryst9080431 ◽

2019 ◽

Vol 9 (8) ◽

pp. 431 ◽

Cited By ~ 2

Author(s):

Li-Lan Tian ◽

Fan Chu ◽

Hu Dou ◽

Lei Li ◽

Qiong-Hua Wang

Keyword(s):

Liquid Crystal ◽

Indium Tin Oxide ◽

Focal Length ◽

Microlens Array ◽

Operating Voltage ◽

Focusing Effect ◽

Horizontal Orientation ◽

Wide Range ◽

Planar Electrodes ◽

The Individual

An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and an LC microlens is generated between the two strip electrodes. For each LC microlens, the gap between the top planar electrodes is directly above the center of the microlens. Unlike the conventional LC lens, the individual LC microlens is not coated with ITO electrodes on the central part of its upper and lower substrates, which helps to maintain the LC’s horizontal orientation. In the voltage-off state, the focal length of the microlens array is infinity because of the homogeneous LC alignment. At a given operating voltage, an ideal gradient refractive index distribution is induced over the homogeneous LC layer, which leads to the focusing effect. The simulation result shows that the focal length of the LC microlens could be gradually drawn to 0.381 mm with a change of voltage.

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Electrically-Tunable Blue Phase Liquid Crystal Microlens Array Based on a Photoconductive Film

Polymers ◽

10.3390/polym12010065 ◽

2020 ◽

Vol 12 (1) ◽

pp. 65 ◽

Cited By ~ 1

Author(s):

Bing-Yau Huang ◽

Shuan-Yu Huang ◽

Chia-Hsien Chuang ◽

Chie-Tong Kuo

Keyword(s):

Refractive Index ◽

Liquid Crystal ◽

Electric Field ◽

Uv Light ◽

Focal Length ◽

Incident Light ◽

Microlens Array ◽

Gradient Distribution ◽

Phase Liquid ◽

Blue Phase

This paper proposes an effective approach to fabricate a blue phase liquid crystal (BPLC) microlens array based on a photoconductive film. Owing to the characteristics of photo-induced conducting polymer polyvinylcarbazole (PVK), in which conductivity depends on the irradiation of UV light, a progressive mask resulting in the variation of conductivity is adopted to produce the gradient distribution of the electric field. The reorientations of liquid crystals according to the gradient distribution of the electric field induce the variation of the refractive index. Thus, the incident light experiences the gradient distribution of the refractive index and results in the focusing phenomenon. The study investigates the dependence of lens performance on UV exposure time, the focal length of the lens, and focusing intensities with various incident polarizations. The BPLC microlens array exhibits advantages such as electrically tunability, polarization independence, and fast response time.

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