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

Abstract

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.

Design of polarimetric camera based on the single-layer twisted nematic liquid crystal device

“…A dualpolarized light-field imaging system constructed by integrating a TNLC microlens array device with common complementary metal oxide silicon (CMOS) sensors is fabricated by Z. Xin 14 , leading to two orthogonally polarized light-field images that can be obtained for direct 3D observation in typical scattering media. Furthermore, M. Chen updated a plenoptic camera prototype using a crucial electrically tunable LC device by constructing two 60-degree TNLCs with an LC microlens array, which allowed for all-in-focus polarimetric imaging, following the acquisition of raw light field images with three polarization states, namely 0-degree and 60-degree, and 120-degree 15 . The polarimetric camera prototype proposed by Xin and Chen shows significant advancements in pixel resolution, target color space and polarization acquisition capabilities compared with the polarimetric camera presented by L. B. Wolff in 1997.…”

中国光学十大进展：可调谐微透镜阵列的研究进展（特邀）

“…9 Microlens arrays in imaging systems. (a) Schematic of the key functioned structure configuration of the camera [82] ; (b) schematic and 3D schematic of a prototype endoscope with a liquid tunablefocus microlens integrated at its end and actuated through IR light [84] 1000002 -10…”

Editorial for the Special Issue on Optics and Photonics in Micromachines

“…In this Special Issue, we are glad to collect 15 research articles covering a broad area, including optical field modulation [ 11 ], laser fabrication techniques [ 12 , 13 ], optical measurement [ 14 , 15 , 16 , 17 , 18 ], on-chip photonic devices [ 19 , 20 , 21 , 22 ], super-resolution imaging [ 23 , 24 ], and related theoretical [ 25 ] investigations.…”

“…Armghan et al [ 19 ] employed a machine-learning method to assist in the design of VCSEL for high-yield optical wireless networks. Chen et al [ 20 ] developed a plenoptic camera based on an electrically tunable liquid crystal with a hexagonal-period liquid crystal array for all-in-focus polarimetric imaging, dedicated to providing more optical information for both scientific and daily applications. Yue et al [ 22 ] proposed a method to integrate 2D optical phased arrays with an on-chip multi-quantum-well laser array heterogeneously based on a silicon photonic platform.…”