Browsing by Author "Javidi, Bahram"

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Analysis of the depth of field of integral imaging displays based on wave optics
(2013-12-16)
Luo, Cheng-Gao
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Xiao, Xiao
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Martinez-Corral, Manuel
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Chen, Chih-Wei
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Javidi, Bahram
In this paper, we analyze the depth of field (DOF) of integral imaging displays based on wave optics. With considering the diffraction effect, we analyze the intensity distribution of light with multiple microlenses and derive a DOF calculation formula for integral imaging display system. We study the variations of DOF values with different system parameters. Experimental results are provided to verify the accuracy of the theoretical analysis. The analyses and experimental results presented in this paper could be beneficial for better understanding and designing of integral imaging displays. (C) 2013 Optical Society of America
Dual layer electrode liquid crystal lens for 2D/3D tunable endoscopy imaging system
(2016-04-18)
Hassanfiroozi, Amir
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Huang, Yi-Pai
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Javidi, Bahram
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Shieh, Han-Ping D.
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光電工程學系
In this paper, we demonstrate a multi-functional liquid-crystal lens (MFLC-lens) based on dual-layer electrode design. Compared with the previous 3D endoscopes, which use double fixed lens capturing, the proposed LC lens is not only switchable between 2D and 3D modes, but also is able to adjust focus in both modes. The diameter of the MFLC-lens is only 1.42mm, which is much smaller than the available 3D endoscopes with double fixed lenses. To achieve the MFLC-lens, a high-resistance layer needs to be coated on the electrode to generate an ideal gradient electric-field distribution, which can induce a lens-like form of LC molecules. The parameters of high-resistive layer are investigated and discussed with an aim to optimize the performance of the MFLC-lens. (C) 2016 Optical Society of America
Dynamic integral imaging display with electrically moving array lenslet technique using liquid crystal lens
(2015-07-13)
Jen, Tai-Hsiang
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Shen, Xin
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Yao, Gang
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Huang, Yi-Pai
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Shieh, Han-Ping D.
Integral imaging (InIm) has been widely investigated for threedimensional (3-D) display applications. Aliasing due to the lenslet arrays is one of the limitations of InIm displays. In this paper, we propose a dynamic InIm display using electrically movable liquid crystal (LC) lens array to implement the moving array lenslet technique (MALT) and to eliminate the multifacet phenomenon in the 3-D images. The improvement of the viewing quality of dynamic InIm display is experimentally verified. (C) 2015 Optical Society of America
Extended depth-of-field 3D endoscopy with synthetic aperture integral imaging using an electrically tunable focal-length liquid-crystal lens
(2015-08-01)
Wang, Yu-Jen
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Shen, Xin
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Lin, Yi-Hsin
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Javidi, Bahram
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光電工程學系
Conventional synthetic-aperture integral imaging uses a lens array to sense the three-dimensional (3D) object or scene that can then be reconstructed digitally or optically. However, integral imaging generally suffers from a fixed and limited range of depth of field (DOF). In this Letter, we experimentally demonstrate a 3D integral-imaging endoscopy with tunable DOF by using a single large-aperture focal-length-tunable liquid crystal (LC) lens. The proposed system can provide high spatial resolution and an extended DOF in synthetic-aperture integral imaging 3D endoscope. In our experiments, the image plane in the integral imaging pickup process can be tuned from 18 to 38 mm continuously using a large-aperture LC lens, and the total DOF is extended from 12 to 51 mm. To the best of our knowledge, this is the first report on synthetic aperture integral imaging 3D endoscopy with a large-aperture LC lens that can provide high spatial resolution 3D imaging with an extend DOF. (C) 2015 Optical Society of America
Extended depth-of-focus 3D micro integral imaging display using a bifocal liquid crystal lens
(2015-02-15)
Shen, Xin
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Wang, Yu-Jen
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Chen, Hung-Shan
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Xiao, Xiao
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Lin, Yi-Hsin
We present a three dimensional (3D) micro integral imaging display system with extended depth of focus by using a polarized bifocal liquid crystal lens. This lens and other optical components are combined as the relay optical element. The focal length of the relay optical element can be controlled to project an elemental image array in multiple positions with various lenslet image planes, by applying different voltages to the liquid crystal lens. The depth of focus of the proposed system can therefore be extended. The feasibility of our proposed system is experimentally demonstrated. In our experiments, the depth of focus of the display system is extended from 3.82 to 109.43 mm. (C) 2015 Optical Society of America
Hexagonal liquid crystal lens array for 3D endoscopy
(2015-01-26)
Hassanfiroozi, Amir
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Huang, Yi-Pai
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Javidi, Bahram
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Shieh, Han-Ping D.
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光電工程學系
A liquid crystal lens array with a hexagonal arrangement is investigated experimentally. The uniqueness of this study exists in the fact that using convex-ring electrode provides a smooth and controllable applied potential profile across the aperture to manage the phase profile. We observed considerable differences between flat electrode and convex-ring electrode; in particular the lens focal length is variable in a wider range from 2.5cm to infinity. This study presents several noteworthy characteristics such as low driving voltage; 30 mu m cell gap and the lens is electrically switchable between 2D/3D modes. We demonstrate a hexagonal LC-lens array for capturing 3D images by using single sensor using integral imaging. (C) 2015 Optical Society of America
Improved Viewing Zones for Projection Type Integral Imaging 3D Display Using Adaptive Liquid Crystal Prism Array
(2014-03-01)
Chen, Chih-Wei
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Cho, Myungjin
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Huang, Yi-Pai
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Javidi, Bahram
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光電工程學系
In this paper, we present a novel projection-type 3-D integral imaging display with an adaptive liquid crystal (LC) prism array. Comparing with conventional integral imaging display, the proposed system demonstrated that the viewing zones for a projection type integral imaging display was successfully extended by time-multiplexed technique and without any mechanical movement. To the best of our knowledge, this is the first report on combining an adaptive LC prism array with the projection-type integral imaging 3-D display. The proposed display is attractive for future wide viewing zone projection-type integral imaging 3-D displays.
LC-lens array with light field algorithm for 3D bio-medical applications
(2016-01-01)
Huang, Yi-Pai
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Hsieh, Po-Yuan
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Hassanfiroozi, Amir
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Martinez, Manuel
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Javidi, Bahram
In this paper, liquid crystal lens (LC-lens) array was utilized in 3D bio-medical applications including 3D endoscope and light field microscope. Comparing with conventional plastic lens array, which was usually placed in 3D endoscope or light field microscope system to record image disparity, our LC-lens array has higher flexibility of electrically changing its focal length. By using LC-lens array, the working distance and image quality of 3D endoscope and microscope could be enhanced. Furthermore, the 2D/3D switching ability could be achieved if we turn off/on the electrical power on LC-lens array. In 3D endoscope case, a hexagonal micro LC-lens array with 350um diameter was placed at the front end of a 1mm diameter endoscope. With applying electric field on LC-lens array, the 3D specimen would be recorded as from seven micro-cameras with different disparity. We could calculate 3D construction of specimen with those micro images. In the other hand, if we turn off the electric field on LC-lens array, the conventional high resolution 2D endoscope image would be recorded. In light field microscope case, the LC-lens array was placed in front of the CMOS sensor. The main purpose of LC-lens array is to extend the refocusing distance of light field microscope, which is usually very narrow in focused light field microscope system, by montaging many light field images sequentially focusing on different depth. With adjusting focal length of LC-lens array from 2.4mm to 2.9mm, the refocusing distance was extended from 1mm to 11.3mm. Moreover, we could use a LC wedge to electrically shift the optics axis and increase the resolution of light field.
Liquid crystal lens array for 3D microscopy and endoscope application
(2016-01-01)
Huang, Yi-Pai
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Hsieh, Po-Yuan
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Hassanfiroozi, Amir
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Chu, Chao-Yu
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Hsuan, Yun
In this paper, we demonstrate two liquid crystal (LC) lens array devices for 3D microscope and 3D endoscope applications respectively. Compared with the previous 3D biomedical system, the proposed LC lens arrays are not only switchable between 2D and 3D modes, but also are able to adjust focus in both modes. The multi-function liquid crystal lens (MFLC-lens) array with dual layer electrode has diameter 1.42 mm, which is much smaller than the conventional 3D endoscope with double fixed lenses. The hexagonal liquid crystal micro-lens array (HLC-MLA) instead of fixed micro-lens array in 3D light field microscope can extend the effective depth of field from 60 um to 780 um. To achieve the LC lens arrays, a high-resistance layer needs to be coated on the electrodes to generate an ideal gradient electric-field distribution, which can induce a lens-like form of LC molecules. The parameters and characteristics of high-resistance layer are investigated and discussed with an aim to optimize the performance of liquid crystal lens arrays.
Liquid Crystal Lens for Axially Distributed Three-Dimensional Sensing
(2013)
Huang, Yi-Pai
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Chen, Chih-Wei
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Cho, Myungjin
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Javidi, Bahram
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光電工程學系
In this paper, we present a novel three-dimensional (3D) sensing system which can demonstrate 3D acquisition. The proposed system is using an electronically tunable liquid crystal (LC) lens with axially distributed sensing method. Therefore, multiple 2D images with slightly different perspectives by varying the focal lengths of the LC lens without mechanical movements of an image sensor can be recorded. And then the 3D images are further reconstructed according to the ray-back projection algorithm. The preliminary functionalities are also demonstrated in this paper. We believe that our proposed system may useful for a compact 3D sensing camera system
Long working range light field microscope with fast scanning multifocal liquid crystal microlens array
(2018-04-16)
Hsieh, Po-Yuan
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Chou, Ping-Yen
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Lin, Hsiu-An
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Chu, Chao-Yu
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Huang, Cheng-Ting
The light field microscope has the potential of recording the all information of biological specimens in real time with a conventional light source. To further extend the depth of field to broaden its applications, in this paper, we proposed a multifocal high-resistance liquid crystal microlens array instead of the fixed microlens array. The developed multifocal liquid crystal microlens array can provide high quality point spread function in multiple focal lengths. By adjusting the focal length of the liquid crystal microlens array sequentially, the total working range of the light field microscope can be much extended. Furthermore, in our proposed system, the intermediate image was placed in the virtual image space of the microlens array, where the condition of the lenslets numerical aperture was considerably smaller. Consequently, a thin-cell-gap liquid crystal microlens array, with fast response time can be implemented for time-multiplexed scanning. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Multidimensional Optical Sensing and Imaging System (MOSIS): From Macroscales to Microscales
(2017-05-01)
Javidi, Bahram
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Shen, Xin
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Markman, Adam S.
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Latorre-Carmona, Pedro
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Martinez-Uso, Adolfo
Multidimensional optical imaging systems for information processing and visualization technologies have numerous applications in fields such as manufacturing, medical sciences, entertainment, robotics, sur-veillance, and defense. Among different 3-D imaging methods, integral imaging is a promising multiperspective sensing and display technique. Compared with other 3-D imaging techniques, integral imaging can capture a scene using an incoherent light source and generate real 3-D images for observation without any special viewing devices. This review paper describes passive multidimensional imaging systems combined with different integral imaging configurations. One example is the integral-imaging-based multidimensional optical sensing and imaging system (MOSIS), which can be used for 3-D visualization, seeing through obscurations, material inspection, and object recognition from microscales to long-range imaging. This system utilizes many degrees of freedom such as time and space multiplexing, depth information, polarimetric, temporal, photon flux and multispectral information based on integral imaging to record and reconstruct the multidimensionally integrated scene. Image fusion may be used to integrate the multidimensional images obtained by polarimetric sensors, multispectral cameras, and various multiplexing techniques. The multidimensional images contain substantially more information compared with 2-D images or conventional 3-D images. In addition, we present recent progress and applications of 3-D integral imaging including human gesture recognition in the time domain, depth estimation, mid-wave-infrared photon counting, 3-D polarimetric imaging for object shape and material identification, dynamic integral imaging implemented with liquid-crystal devices, and 3-D endoscopy for healthcare applications.
Security authentication using phase-encoded nanoparticle structures and polarized light
(2015-01-15)
Carnicer, Artur
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Hassanfiroozi, Amir
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Latorre-Carmona, Pedro
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Huang, Yi-Pai
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Javidi, Bahram
Phase-encoded nanostructures such as quick response (QR) codes made of metallic nanoparticles are suggested to be used in security and authentication applications. We present a polarimetric optical method able to authenticate random phase-encoded QR codes. The system is illuminated using polarized light, and the QR code is encoded using a phase-only random mask. Using classification algorithms, it is possible to validate the QR code from the examination of the polarimetric signature of the speckle pattern. We used Kolmogorov-Smirnov statistical test and Support Vector Machine algorithms to authenticate the phase-encoded QR codes using polarimetric signatures. (C) 2015 Optical Society of America
Three-dimensional imaging with axially distributed sensing using electronically controlled liquid crystal lens
(2012-10-01)
Chen, Chih-Wei
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Cho, Myungjin
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Huang, Yi-Pai
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Javidi, Bahram
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土木工程學系
In this Letter, we present a three-dimensional (3D) imaging system with axially distributed sensing (ADS) using an electronically controlled liquid crystal (LC) lens. The proposed system performed an optical image acquisition by varying the focal lengths of the LC lens without mechanical movements of an image sensor. Multiple images with slightly different perspectives were experimentally recorded, and the 3D images were reconstructed according to the ray backprojection algorithm. To the best of our knowledge, this is the first report on 3D ADS using a LC lens. The proposed system is attractive for compact 3D sensing camera systems. (C) 2012 Optical Society of America
Untitled
(2015-10-01)
Javidi, Bahram
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Martinez-Corral, Manuel
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Ferraro, Pietro
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Hua, Hong
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Huang, Yi Pai