Browsing by Author "Li, Jie-En"

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Accessing Refractive Errors via Eccentric Infrared Photorefraction Based on Deep Learning
(2019-01-01)
Yang, Chia-Chi
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Su, Jian-Jia
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Li, Jie-En
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Zhu, Zhi-Yu
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Tseng, Jin-Shing
Eccentric infrared photorefraction is an attractive vision screening method which is widely used for uncooperative subjects, such as infants and toddlers. Unlike conventional slope-based photorefraction, a deep neural network is used to predict refractive error in this study. Total 1216 ocular image were collected by a homemade photorefraction device, whose corresponding refractive error was measured by a commercial autorefractor device, to create a series of dataset for our deep neural network. The mean squared error of the preliminary result is +/- 0.9 diopter, which indicates its feasibility and can be improved with bigger database.
Automatic Organic Light-emitting Diode Display Mura Detection Model based on Human Visual Perception and Multi-resolution
(2019-01-01)
Zhu, Zhi-Yu
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Li, Jie-En
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Hsieh, Po-Yuan
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Su, Jian-Jia
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Tien, Chung-Hao
Organic light emitting diode generally has serious non-uniformity phenomena due to the instability of organic processing, called Mura. In this paper, we propose an automatic Mura detection model to mimic the human perception and detect Mura pixel-wisely. First, we extract regions of interest from the original image with different sizes of windows, and then we verify these regions by SEMU criterion. Consequently, we implement human visual properties based on the contrast sensitivity function filtering and ModelFest matching to segment Mura regions. As the result, our approach can successfully detect Mura with various sizes and shapes, which could have a great impact on the display industry.
Experimental method of optical coherence characterization in phase-space measurement
(2015-01-01)
Li, Jie-En
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Fu, Jhih-Syuan
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Hsiao, Ming-Shu
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Tien, Chung-Hao
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光電工程學系
A novel approach of phase-space measurement made its debut with the experimental result. We first designed an experiment based on the Young's interferometer to characterization the optical coherence property of light source. A well-known algorithm called Hough transformation was applied to deal with the misalignment of micro-lens array by post-processing. The phase-space image of plane wave was then reconstructed from the realigned raw image. Finally, the properties of this system were discussed.
Fundus photography with subpixel registration of correlated laser speckle images
(2018-09-01)
Li, Jie-En
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
In this paper, we propose multiple modalities based on laser speckle correlation and image registration to enhance the visibility of the fundus without a scanning interferometric scenario, resulting in robustness against intra frame noises induced by inevitable movement. The experimental results showed, with the features from laser speckle contrast imaging (LSCI), that the quality of images obtained using a conventional imaging system could be enhanced. Moreover, by applying the image registration process, we successfully eliminated the inter frame blurring caused by eye movements in an in vivo experiment. The concept was proven when the image contrast of a vascular feature was improved by 1.00x-2.75x. (c) 2018 The Japan Society of Applied Physics
Measurement of second-order phenomenon with spatial light modulator
(2018-01-01)
Li, Jie-En
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
High-order statistical properties of wavefield had been proven to have great influences in the realm of optics. For example, the speckle pattern induced by multi-interference of a coherent light source could be utilized to reconstruct the speckle flowgraphy either in ocular or cerebral blood flow. Such speckle pattern could also be used in depth estimation or optical positioning system. Recently, Kondakci et al. proposed a far-field lensless identification system based on measuring the complex coherence factor (the second-order phenomenon of light) of the field scattering off an obstructive object, which developed another possibility in optical imaging. However, their measurement was based on digital micro-mirror device, which restricted the flexibility of such optical system. Therefore, in this work, we designed an optical system to dynamically measure the complex coherence factor of a Schell-model and quasi-homogeneous beam via spatial light modulator. By analyzing the pixelated structure in theoretically and numerically, it was found that the fill factor of spatial light modulator would not affect the second-order characteristics of incident field even if its first-order characteristics were different. Our experimental results showed this system indeed had a good performance in the measurement of complex coherence factor. We believe the proposed optical system can help the lensless identification. Moreover, this system can be further improved by replacing the reflective-type spatial light modulator with transmitted-type, which will significantly increase the flexibility of optical instrument and will definitely have a great impact on other optical technologies.
Plasmonic rainbow rings induced by white radial polarization
(2012-04-01)
Lan, Tzu-Hsiang
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Chung, Yi-Kuan
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Li, Jie-En
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Tien, Chung-Hao
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光電工程學系
This Letter presents a scheme to embed both angular/spectral surface plasmon resonance (SPR) in a unique far-field rainbow feature by tightly focusing (effective NA = 1.45) a polychromatic radially polarized beam on an Au(20 nm)/SiO2(500 nm)/Au(20 nm) sandwich structure. Without the need for angular or spectral scanning, the virtual spectral probe snapshots a wide operation range (n = 1-1.42; lambda = 400-700 nm) of SPR excitation in a locally nanosized region. Combined with the high-speed spectral analysis, a proof-of-concept scenario was given by monitoring the NaCl liquid concentration change in real time. The proposed scheme will certainly has a promising impact on the development of objective-based SPR sensor and biometric studies due to its rapidity and versatility. (C) 2012 Optical Society of America
Recovery of Phase Modulation via Residual Neural Network
(2019-01-01)
Yao, Yun-Zhen
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Su, Jian-Jia
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Li, Jie-En
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Zhu, Zhi-Yu
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Tien, Chung-Hao
An approach for recovering the phase information from the detected intensity was proposed in this work. Unlike the conventional approach based on the Gerchberg-Saxton algorithm, the proposed approach recovered the phase information via an alternative technique in the realm of deep learning, the residual neural network. The database we utilized to train the network was collected by a Michelson-based interferometer, where a spatial light modulator was implemented to provide the phase modulation as the phase object. As the result, the mean absolute error of each pixel was 0.0614 pi.
The study of pixelated sampling and its influences on the 2nd-order spatial coherence measurement
(2018-09-15)
Li, Jie-En
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
Since the measurement of spatial coherence requires multiple sampling to acquire the complex coherence factor of a wavefield, it is convenient to accomplish such dynamic work by a non-redundant multi-slit through a programmable device such as spatial light modulator (SLM). In this study, we examined the influence of SLM-like pixelated structure, parameterized by whose fill factor, on both intensity distribution (first-order statistics) and complex coherence factor (second-order statistics). Based on the generalized Van Cittert-Zernike theorem that as the source satisfied the quasi-homogeneous condition, the coherence factor of the wavefield was irrelevant to the pixelated sampling structure. The inference was validated by a SLM-based experiment from a pseudothermal light source. We expected this work to be useful for future dynamic coherence measurement.