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

Chen, Mingce; He, Wenda; Dong, Wei; Hu, Cong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

doi:10.3390/s20154142

Cited by 21 publications

(7 citation statements)

References 45 publications

(63 reference statements)

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“…The field of LC-tunable lenses is very active at the moment 25 , 26 , as they can be used in ophthalmic applications 27 – 29 , mobile phones 30 , autostereoscopic devices 31 , 32 , plenoptic capture systems 33 , 34 , virtual reality displays 35 , to name some key enabled applications. In recent years, numerous structures have been proposed, e.g., by using curved electrodes 36 , 37 , built-in dielectric layers 38 – 40 , multielectrodes 41 – 44 and modal lenses 27 , 30 , 45 , 46 .…”

Section: Introductionmentioning

confidence: 99%

A high birefringence liquid crystal for lenses with large aperture

Bennis

Jankowski

Strzeżysz

et al. 2022

Sci Rep

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This work presents the application of an experimental nematic liquid crystal (LC) mixture (1929) in a large aperture lens. The LC material is composed of terphenyl and biphenyl derivatives compounds with an isothiocyanate terminal group and fluorinated lateral substituents. The substitution with a strongly polar isothiocyanate group and an aromatic rigid core provides $$\pi$$ π -electron coupling, providing high birefringence ($$\Delta n = 0.3375$$ Δ n = 0.3375 at 636 nm and 23 °C) and low viscosity ($$\eta$$ η = 17.03 mPa s). In addition, it also shows high values of birefringence at near infrared (0.318 at 1550 nm). The synthesis process is simple when comparing materials with high melting temperatures. The excellent properties of this LC mixture are demonstrated in a large aperture LC-tunable lens based on a transmission electrode structure. Thanks to the particular characteristics of this mixture, the optical power is high. The high birefringence makes this LC of specific interest for lenses and optical phase modulators and devices, both in the visible and infrared regions.

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Section: Introductionmentioning

confidence: 99%

A high birefringence liquid crystal for lenses with large aperture

Bennis

Jankowski

Strzeżysz

et al. 2022

Sci Rep

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“…The LCMLA is another key component of the proposed plenoptic camera. Recently, the LCMLA-based plenoptic cameras have attracted a lot of research interests [30,31] owing to several obvious advantages including easy integration with other functioned structure or devices, 2D/3D switchable mode, ease of fabricating [32,33], and the excellent tunability with driving electric field applied [34][35][36][37][38]. In addition, the previously proposed the micrometric LC bubbles do not require the patterned electrode and thus remarkably improve the optical resolution of the LCMLA [39].…”

Section: Methodsmentioning

confidence: 99%

All-In-Focus Polarimetric Imaging Based on an Integrated Plenoptic Camera with a Key Electrically Tunable LC Device

Chen

et al. 2022

Micromachines

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In this paper, a prototyped plenoptic camera based on a key electrically tunable liquid-crystal (LC) device for all-in-focus polarimetric imaging is proposed. By using computer numerical control machining and 3D printing, the proposed imaging architecture can be integrated into a hand-held prototyped plenoptic camera so as to greatly improve the applicability for outdoor imaging measurements. Compared with previous square-period liquid-crystal microlens arrays (LCMLA), the utilized hexagonal-period LCMLA has remarkably increased the light utilization rate by ~15%. Experiments demonstrate that the proposed imaging approach can simultaneously realize both the plenoptic and polarimetric imaging without any macroscopic moving parts. With the depth-based rendering method, both the all-in-focus images and the all-in-focus degree of linear polarization (DoLP) images can be obtained efficiently. Due to the large depth-of-field advantage of plenoptic cameras, the proposed camera enables polarimetric imaging in a larger depth range than conventional 2D polarimetric cameras. Currently, the raw light field images with three polarization states including I0 and I60 and I120 can be captured by the proposed imaging architecture, with a switching time of several tens of milliseconds. Some local patterns which are selected as interested target features can be effectively suppressed or obviously enhanced by switching the polarization state mentioned. According to experiments, the visibility in scattering medium can also be apparently improved. It can be expected that the proposed polarimetric imaging approach will exhibit an excellent development potential.

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“…However, a conventional light field camera is inherently limited in shallow depth of field (DoF) because the MLA has a finite DoF. To address this problem, extensive research has been conducted to extend the DoF, including the adoption of multi-focal MLA [13][14][15] and focal length modulation based on liquid-crystal MLA (LC-MLA) [16,17]. Although multi-focal MLA and LC-MLA successfully extend the DoF to some extent, there still exist difficulties in practical application because of their complex manufacturing process, low spatial resolution in multi-focal MLA, inconsistent focal length tendency at low voltage and/or relatively low transparency in LC-MLA [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Vari-Focal Light Field Camera for Extended Depth of Field

Kim

Chang

et al. 2021

Micromachines

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The light field camera provides a robust way to capture both spatial and angular information within a single shot. One of its important applications is in 3D depth sensing, which can extract depth information from the acquired scene. However, conventional light field cameras suffer from shallow depth of field (DoF). Here, a vari-focal light field camera (VF-LFC) with an extended DoF is newly proposed for mid-range 3D depth sensing applications. As a main lens of the system, a vari-focal lens with four different focal lengths is adopted to extend the DoF up to ~15 m. The focal length of the micro-lens array (MLA) is optimized by considering the DoF both in the image plane and in the object plane for each focal length. By dividing measurement regions with each focal length, depth estimation with high reliability is available within the entire DoF. The proposed VF-LFC is evaluated by the disparity data extracted from images with different distances. Moreover, the depth measurement in an outdoor environment demonstrates that our VF-LFC could be applied in various fields such as delivery robots, autonomous vehicles, and remote sensing drones.

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

Cited by 21 publications

References 45 publications

A high birefringence liquid crystal for lenses with large aperture

A high birefringence liquid crystal for lenses with large aperture

All-In-Focus Polarimetric Imaging Based on an Integrated Plenoptic Camera with a Key Electrically Tunable LC Device

Vari-Focal Light Field Camera for Extended Depth of Field

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