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High-speed, high-precision focal length measurement using double-hole mask and advanced image sensor software

ISA TRANSACTIONS 2018年 74卷 239-244页

作者： Binh Xuan Cao Phuong Le Hoang Ahn, Sanghoon Kim, Jeng-o Kang, Heeshin Noh, Jiwhan KIMM Dept Laser & Elect Beam Applicat Daejeon 34103 South Korea Korea Univ Sci & Technol UST Dept Nanomechatron Daejeon 34113 South Korea Korea Adv Inst Sci & Technol Dept Mat Sci & Engn Daejeon 34141 South Korea

A cutting-edge precision technique for computation of focal length of a positive lens with double-hole mask is described. The technique is simple and versatile due to incorporation of the updated functions of image sensor device that supports reading the distance between beam spots instantaneously while the position of the specimen is being changed, as well as the reduction in several challenging measurement steps. Furthermore, this technique does not require prior knowledge of distances in the optical setup. High accuracy in focal-length measurement is obtained by precise beam spot distance analysis using image sensor integrated software. The acquired data exhibit considerably high precision and reproducibility. (C) 2018 ISA. Published by Elsevier Ltd. All rights reserved.

关键词： Focal length measurement image sensor Double-hole mask Laser micromachining

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Interpixel Interference Mitigation in Visible Light Communication Using image sensor

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IEEE ACCESS 2018年 6卷 45543-45551页

作者： Dat Vuong Yoo, Myungsik Soongsil Univ Sch Elect Engn Seoul 06978 South Korea

To improve the data rate in a camera-based visible light communication system, multiple LEDs in an LED array are used to transmit multiple bits in one frame. The problem is that LEDs are always captured in the image with some degree of blooming effect. This effect increases the intensity of pixels surrounding the origin LEDs in the image. When multiple LEDs are used, the blooming effect from all LEDs causes the interpixel interference (IPI) problem that greatly degrades the quality of the received signal. This paper analyzes the blooming effect and finds that the IPI problem increases when the number of "ON" LEDs in the array increases. Through the analysis, this paper proposes a differential coding to minimize the number of "ON" LEDs in every transmitted frame and thus minimize the IPI effect. The proposed scheme is then verified through simulations. The results show that a lower bit error rate, which indicates a better signal quality, can be achieved by applying the proposed scheme.

关键词： VLC LED image sensor differential coding interference

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Integrated Polarization Analyzing CMOS image sensor for Material Classification

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IEEE sensorS JOURNAL 2011年第8期11卷 1692-1703页

作者： Sarkar, Mukul Bello, David San Segundo van Hoof, Chris Theuwissen, Albert IMEC NL-5656 AE Eindhoven Netherlands Delft Univ Technol Elect Instrumentat Lab NL-2628 CD Delft Netherlands IMEC B-3001 Louvain Belgium Harvest Imaging B-3960 Bree Belgium

Material classification is an important application in computer vision. The inherent property of materials to partially polarize the reflected light can serve as a tool to classify them. In this paper, a real-time polarization sensing CMOS image sensor using a wire grid polarizer is proposed. The image sensor consist of an array of 128 x 128 pixels, occupies an area of 5 x 4 mm(2) and it has been designed and fabricated in a 180-nm CMOS process. We show that this image sensor can be used to differentiate between metal and dielectric surfaces in real-time due to the different nature in partially polarizing the specular and diffuse reflection components of the reflected light. This is achieved by calculating the Fresnel reflection coefficients, the degree of polarization and the variations in the maximum and minimum transmitted intensities for varying specular angle of incidence. Differences in the physical parameters for various metal surfaces result in different surface reflection behavior, influencing the Fresnel reflection coefficients. It is also shown that the image sensor can differentiate among various metals by sensing the change in the polarization Fresnel ratio.

关键词： degree of polarization Fresnel reflection coefficients image sensor material classification polarization stokes parameters wire grid polarizer

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Applications of the integrated high-performance CMOS image sensor to range finders - From optical triangulation to the automotive field

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sensorS 2008年第3期8卷 1719-1739页

作者： Wu, Jih-Huah Pen, Cheng-Chung Jiang, Joe-Air Ming Chuan Univ Dept Biomed Engn Tao Yuan 333 Taiwan Natl Cent Univ Dept Opt & Photon Chungli 320 Taoyuan Taiwan Natl Taiwan Univ Dept Bioind Mechatron Engn Taipei 106 Taiwan

With their significant features, the applications of complementary metal-oxide semiconductor (CMOS) image sensors covers a very extensive range, from industrial automation to traffic applications such as aiming systems, blind guidance, active/passive range finders, etc. In this paper CMOS image sensor-based active and passive range finders are presented. The measurement scheme of the proposed active/passive range finders is based on a simple triangulation method. The designed range finders chiefly consist of a CMOS image sensor and some light sources such as lasers or LEDs. The implementation cost of our range finders is quite low. image processing software to adjust the exposure time ( ET) of the CMOS image sensor to enhance the performance of triangulation-based range finders was also developed. An extensive series of experiments were conducted to evaluate the performance of the designed range finders. From the experimental results, the distance measurement resolutions achieved by the active range finder and the passive range finder can be better than 0.6% and 0.25% within the measurement ranges of 1 to 8 m and 5 to 45 m, respectively. Feasibility tests on applications of the developed CMOS image sensor-based range finders to the automotive field were also conducted. The experimental results demonstrated that our range finders are well-suited for distance measurements in this field.

关键词： complementary metal-oxide semiconductor (CMOS) distance measurement image sensor range finder triangulation method

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Improved Denoising via Poisson Mixture Modeling of image sensor Noise

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IEEE TRANSACTIONS ON image PROCESSING 2017年第4期26卷 1565-1578页

作者： Zhang, Jiachao Hirakawa, Keigo Univ Dayton Dayton OH 45469 USA Nanjing Univ Sci & Technol Dept Automat Nanjing 210094 Jiangsu Peoples R China Univ Dayton Dept Elect & Comp Engn Dayton OH 45469 USA

This paper describes a study aimed at comparing the real image sensor noise distribution to the models of noise often assumed in image denoising designs. A quantile analysis in pixel, wavelet transform, and variance stabilization domains reveal that the tails of Poisson, signal-dependent Gaussian, and Poisson-Gaussian models are too short to capture real sensor noise behavior. A new Poisson mixture noise model is proposed to correct the mismatch of tail behavior. Based on the fact that noise model mismatch results in image denoising that undersmoothes real sensor data, we propose a mixture of Poisson denoising method to remove the denoising artifacts without affecting image details, such as edge and textures. Experiments with real sensor data verify that denoising for real image sensor data is indeed improved by this new technique.

关键词： image denoising image sensor Poisson

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Biologically Inspired CMOS image sensor for Fast Motion and Polarization Detection

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IEEE sensorS JOURNAL 2013年第3期13卷 1065-1073页

作者： Sarkar, Mukul Bello, David San Segundo van Hoof, Chris Theuwissen, Albert J. P. IMEC NL-5656 AE Eindhoven Netherlands Delft Univ Technol Elect Instrumentat Lab NL-2628 CD Delft Netherlands IMEC B-3001 Louvain Belgium Harvest Imaging B-3960 Bree Belgium

A complementary-metal-oxide semiconductor (CMOS) image sensor replicating the perception of vision in insects is presented for machine vision applications. The sensor is equipped with in-pixel analog and digital memories that allow in-pixel binarization in real time. The binary output of the pixel tries to replicate the flickering effect of an insect's eye to detect the smallest possible motion based on the change in state of each pixel. The pixel level optical flow generation reduces the need for digital hardware and simplifies the process of motion detection. A built-in counter counts the changes in states for each row to estimate the direction of the motion. The designed image sensor can also sense polarization information in real time using a metallic wire grid micropolarizer. An extinction ratio of 7.7 is achieved. The 1-D binary optical flow is shown to vary with the polarization angle of the incoming light ray. The image sensor consists of an array of 128 x 128 pixels, occupies an area of 5 x 4 mm(2) and it is designed and fabricated in a 180-nm CMOS process.

关键词： Analog and digital polarization collision detection image sensor motion detection optical flow polarization wire grid polarizer

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CMOS Demodulation image sensor for Nanosecond Optical Waveform Analysis

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IEEE sensorS JOURNAL 2013年第5期13卷 1487-1497页

作者： Bonjour, Lysandre-Edouard Beyeler, David Blanc, Nicolas Kayal, Maher Swiss Ctr Elect & Microtechnol CSEM SA CH-8002 Zurich Switzerland Swiss Fed Inst Technol Elect Lab CH-1015 Lausanne Switzerland

An image sensor with 256 x 256 pixels and a pitch of 6.3 mu m, suitable for resolving ultrashort optical phenomena, is developed. It is based on a standard CMOS process with pinned photodiode option. The pixel comprises three transfer gates to allow versatile sensor operation whereas repetitive exposure and integration are used to increase the lowest signal level that can be detected. The image sensor is fully functional and demonstrates the ability to demodulate signals in the time-domain with contrast higher than 92% up to 100 MHz. Algorithms for fluorescence lifetime imaging microscopy and three-dimensional time-of-flight imaging are proposed. They allow measurements to be insensitive to background light, subsurface leakage, dark current leakage, and subthreshold leakage of the transfer gates. Lifetimes of free quantum dots are resolved using time-domain demodulation. Range imaging is also shown to be possible with frequency-domain demodulation although background light cannot be suppressed efficiently in the present implementation of the image sensor due to the limited full well capacity.

关键词： Buried photodiode CMOS imager FLS FLIM fluorescence decay fluorescence lifetime image sensor phosphorescence lifetime pinned photodiode time-of-flight TOF triplet state

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Noise Reduction Method for image Signal Processor Based on Unified image sensor Noise Model

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IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS 2013年第5期E96D卷 1152-1161页

作者： Baek, Yeul-Min Kim, Whoi-Yul Hanyang Univ Seoul 133791 South Korea

The noise in digital images acquired by image sensors has complex characteristics due to the variety of noise sources. However, most noise reduction methods assume that an image has additive white Gaussian noise (AWGN) with a constant standard deviation, and thus such methods are not effective for use with image signal processors (ISPs). To efficiently reduce the noise in an ISP, we estimate a unified noise model for an image sensor that can handle shot noise, dark-current noise, and fixed-pattern noise (FPN) together, and then we adaptively reduce the image noise using an adaptive Smallest Univalue Segment Assimilating Nucleus (SUSAN) filter based on the unified noise model. Since our noise model is affected only by image sensor gain, the parameters for our noise model do not need to be re-configured depending on the contents of image Therefore, the proposed noise model is suitable for use in an ISP. Our experimental results indicate that the proposed method reduces image sensor noise efficiently.

关键词： image signal processor noise modeling denoising image sensor SUSAN filtering

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A 0.5 V Sub-Microwatt CMOS image sensor With Pulse-Width Modulation Read-Out

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IEEE JOURNAL OF SOLID-STATE CIRCUITS 2010年第4期45卷 759-767页

作者： Hanson, Scott Foo, ZhiYoong Blaauw, David Sylvester, Dennis Univ Michigan Ann Arbor MI 48109 USA

Energy minimization is a critical goal in size-constrained wireless sensors. Sensing elements are traditionally power hungry and require special attention in low energy systems. In this work, we study ultra-low power image sensors. In particular, we explore the use of aggressive voltage scaling in CMOS image sensors for applications ranging from retinal prostheses to battlefield monitoring and surveillance. We begin with a discussion of the challenges faced by a traditional 3T active pixel sensor as the supply voltage scales to 0.5 V and below. We then discuss an image sensor with pulse-width modulation read-out that is optimized for 0.5 V operation. A 0.13 mu m test-chip with a 128 x 128 pixel array is shown to be functional with V-dd as low as 0.45 V with energy consumption of 140 nJ/frame at V-dd = 0.5 V (8.5 frames per second) and power consumption of only 700 nW at V-dd = 0.5 V (0.5 frames per second). A focus is also placed on quantifying the noise implications of low voltage operation on the test-chip, which has a measured signal-to-noise ratio of 23.4 dB in saturation at V-dd = 0.5 V.

关键词： image sensor low power low voltage

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High-Performance 2D MoS₂ Phototransistor for Photo Logic Gate and image sensor

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ACS PHOTONICS 2018年第12期5卷 4745-4750页

作者： Lee, Young Tack Kang, Ji-Hoon Kwak, Kisung Ahn, Jongtae Choi, Hyun Tae Ju, Byeong-Kwon Shokouh, Seyed Hossein Im, Seongil Park, Min-Chul Hwang, Do Kyung Inha Univ Dept Elect Engn Incheon 22212 South Korea Korea Inst Sci & Technol Ctr Optoelect Mat & Devices Postsilicon Semicond Inst KIST Sch Seoul 02792 South Korea Korea Inst Sci & Technol KIST Sch Div Nano & Informat Technol Seoul 02792 South Korea Korea Univ Coll Engn Display & Nanosyst Lab Seoul 02841 South Korea Yonsei Univ Inst Phys & Appl Phys Seoul 03722 South Korea

Two-dimensional (2D) MoS2 is a representative n-type transition-metal dichalcogenide (TMD) semiconductor that has great potential for future nanoscale electronic and optoelectronic applications. Here, we report a high-performance MoS2 phototransistor that exhibits a photoresponse in the 400-700 nm range with the maximum responsivity of over 1 X 10(4) A/W. As a more sophisticated optoelectronic application than a simple unit device, it is implemented in a photoinverter (NOT logic gate) connected to an external resistor, which clearly shows photoinduced static and dynamic characteristics. Furthermore, we demonstrate a prototype visible imager using the MoS2 photoinverter as imaging pixels as an excellent example of advanced developments in an optoelectronic system based on the 2D semiconductors.

关键词： two-dimensional van der Waals materials MoS2 graphene contact phototransistor photoinverter image sensor

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