scholarly journals Depth-of-Field-Extended Plenoptic Camera Based on Tunable Multi-Focus Liquid-Crystal Microlens Array

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4142 ◽  
Author(s):  
Mingce Chen ◽  
Wenda He ◽  
Dong Wei ◽  
Chai Hu ◽  
Jiashuo Shi ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Radiation Power ◽  
Focal Length ◽  
Microlens Array ◽  
Oxide Semiconductor ◽  
Depth Of Field ◽  
Digital Refocusing ◽  
Wide Range ◽  
Cmos Sensor ◽  
Plenoptic Camera

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.

scholarly journals Electrically Tunable-Focusing Liquid Crystal Microlens Array with Simple Electrode

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 431 ◽  
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.

scholarly journals Generating Bessel beams with broad depth-of-field by using phase-only acoustic holograms

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sergio Jiménez-Gambín ◽  
Noé Jiménez ◽  
José M. Benlloch ◽  
Francisco Camarena
Keyword(s):  
Field Distribution ◽  
Focal Length ◽  
Bessel Beam ◽  
Transverse Field ◽  
High Order ◽  
Depth Of Field ◽  
Uniform Field ◽  
Axial Distribution ◽  
Bessel Beams ◽  
Wide Range

AbstractWe report zero-th and high-order acoustic Bessel beams with broad depth-of-field generated using acoustic holograms. While the transverse field distribution of Bessel beams generated using traditional passive methods is correctly described by a Bessel function, these methods present a common drawback: the axial distribution of the field is not constant, as required for ideal Bessel beams. In this work, we experimentally, numerically and theoretically report acoustic truncated Bessel beams of flat-intensity along their axis in the ultrasound regime using phase-only holograms. In particular, the beams present a uniform field distribution showing an elongated focal length of about 40 wavelengths, while the transverse width of the beam remains smaller than 0.7 wavelengths. The proposed acoustic holograms were compared with 3D-printed fraxicons, a blazed version of axicons. The performance of both phase-only holograms and fraxicons is studied and we found that both lenses produce Bessel beams in a wide range of frequencies. In addition, high-order Bessel beam were generated. We report first order Bessel beams that show a clear phase dislocation along their axis and a vortex with single topological charge. The proposed method may have potential applications in ultrasonic imaging, biomedical ultrasound and particle manipulation applications using passive lenses.

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

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 65 ◽  
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.

Liquid-crystal lens with a focal length that is variable in a wide range

2004 ◽  
Vol 43 (35) ◽  
pp. 6407 ◽  
Author(s):  
Mao Ye ◽  
Bin Wang ◽  
Susumu Sato
Keyword(s):  
Liquid Crystal ◽  
Focal Length ◽  
Wide Range ◽  
Liquid Crystal Lens

Fabrication of a focal length variable microlens array based on a nematic liquid crystal

2003 ◽  
Vol 21 (1-3) ◽  
pp. 643-646 ◽  
Author(s):  
Yoonseuk Choi ◽  
Jae-Hong Park ◽  
Jae-Hoon Kim ◽  
Sin-Doo Lee
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Focal Length ◽  
Microlens Array ◽  
Length Variable

An electrically tunable plenoptic camera using a liquid crystal microlens array

2015 ◽  
Vol 86 (5) ◽  
pp. 053101 ◽  
Author(s):  
Yu Lei ◽  
Qing Tong ◽  
Xinyu Zhang ◽  
Hongshi Sang ◽  
An Ji ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Microlens Array ◽  
Plenoptic Camera

scholarly journals A Sensor Image Super-Resolution via Advanced Generative Adversarial Network

2018 ◽  
Author(s):  
Shiping Wang ◽  
Linyuan He ◽  
Duyan Bi ◽  
Chen Wang
Keyword(s):  
Weather Condition ◽  
Super Resolution ◽  
Image Sensor ◽  
Oxide Semiconductor ◽  
Learning Ability ◽  
Generative Adversarial Networks ◽  
Great Success ◽  
Adversarial Networks ◽  
Wide Range ◽  
Cmos Sensor

Complementary Metal-Oxide-Semiconductor (CMOS) is a typical image sensor that has a wide range of applications. However, considering the limitations of the weather condition and hardware cost, it is hard to capture high-resolution images by CMOS sensor. Recently, Super-Resolution (SR) techniques for image restoration has been gaining attentions due to its excellent performance. Under the powerful learning ability, Generative Adversarial Networks (GANs) have been proved to achieve great success. In this paper, we propose the Advanced Generative Adversarial Networks (AGAN) to efficiently correct these issues; 1) we design a Laplacian pyramid framework as pre-trained module, which is beneficial to provide multi-scale features for our input. 2) at each feature block, a convolutional skip-connections network, which may contain some latent information, is significant for generative model to reconstruct a plausible-looking image; 3) considering that edge details usually play an important role in image generation, a novel perceptual loss function is defined to train and seek optimal parameters. It is effective to achieve excellent and compelling quality captured by CMOS sensor. Quantitative and qualitative evaluations have been demonstrated that our algorithm not only fully takes advantage of Convolutional Neural Networks (CNNs) to improve the image quality, but also performs better than previous GAN algorithms for super-resolution task.

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