• Title/Summary/Keyword: Visible light identification

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Reducing the Effects of Noise Light Using Inter-Bit Noise Detection in a Visible Light Identification System (가시광 무선인식장치에서 비트간 잡음검출에 의한 잡음광의 영향 감소)

  • Hwang, Da-Hyun;Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.20 no.6
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    • pp.412-419
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    • 2011
  • In this paper, we used the inter-bit noise detection method in order to reduce the effects of noise light in a visible light identification system that uses a visible LED as a carrier source. A visible light identification system consists of a reader and a transponder. When the enable signal from the reader is detected, the transponder encodes the response data in RZ(Return-to-Zero) bit stream and sends response signal by modulating a visible LED. The reader detects the response signal mixed with noise light, samples the noise voltage in each blank low time between data bits of the RZ signal, and recovers the original data by subtracting the sampled noise from the received signal. In experiments, we improved the signal-to-noise ratio by 20dB using the inter-bit noise detection method.

A Passive Transponder for Visible Light Identification Using a Solar Cell (솔라셀을 이용한 가시광 인식용 수동형 트랜스폰더)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.23 no.4
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    • pp.238-244
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    • 2014
  • In this paper, we introduce a new passive transponder that operates without external power in a visible light identification system. The transponder consists of a solar cell, a photodiode, a microprocessor, and a visible LED. When a reader sends light to the transponder, the solar cell generates current from the reader light and supplies power to the other elements in the transponder. At the same time, the photodiode detects the pulse in the reader light and initiates a microprocessor to generate and send a responding light to the reader. In experiments, we realized a passive transponder using a solar cell that operated at a distance of 1m without external power.

Flicker Prevention Through Edge-Pulse Modulation in a Visible Light Identification System (가시광 무선인식장치에서 가장자리 펄스변조를 이용한 플리커 방지)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.29 no.3
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    • pp.180-186
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    • 2020
  • In this study, we applied edge-pulse modulation to prevent the flicker of light-emitting diode (LED) light in a visible light identification system. In the visible light transmitter, positive pulses were transmitted at the edges of the low-to-high transition points, and negative pulses were transmitted at the edges of the high-to-low transition points of the non-return-to-zero (NRZ) data waveforms. In the visible light receiver, the NRZ waveforms were regenerated by making low-to-high and high-to-low transitions at the point of the positive and negative pulses, respectively. This method has two advantages. First, it ensures that the LED light is flicker-free because the average optical power of the LED was kept constant during data transmission in the transmitter. Second, the 120 Hz optical noise from the adjacent lighting lamps was easily cut off using a simple RC-high pass filter in the receiver.

Visible Light Identification System Using Optoelectronic Feedback of A Lighting LED (조명용 LED의 광전궤환을 이용한 가시광 무선인식장치)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.20 no.3
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    • pp.193-198
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    • 2011
  • In this paper, we used optoelectronic feedback to generate the carrier frequency for the ASK modulation of a lighting LED. A solar cell was used for photo-detector in the feedback circuit, and the LED light was ASK modulated by controlling the ON/OFF state of the switch that is installed in the feedback loop. The oscillation frequency of the optoelectronic feedback loop was about 50 kHz and the data rate of the ASK modulation was 9.6 kbps. In experiments, the optoelectronic feedback circuit was used for the ASK modulation of a lighting LED in the transponder of a visible light identification system, and data exchange between the transponder and the reader was successfully carried out.

A Passive Transponder for Visible Light Identification Using Ultrasonic wave (초음파를 이용한 가시광인식 수동형 트랜스폰더)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.26 no.3
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    • pp.192-198
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    • 2017
  • In this paper, we newly developed a passive transponder for visible light identification (VLID) using ultrasonic wave. The solar cell in the transponder receives the reader light and generates current for supplying power to the transponder circuit. At the same time the solar cell detects the interrogating signal in the visible light from the reader. The transponder recognizes the interrogating signal and generates the responding signal using ultrasonic wave. In experiments, we used 40 kHz ultrasonic wave for the responding signal from the transponder. The maximum read distance was about 3.4 m when the transponder was exposed to the reader light of 24W LED array.

Visible Light Identification System for Smart Door Lock Application with Small Area Outdoor Interface

  • Song, Seok-Jeong;Nam, Hyoungsik
    • Current Optics and Photonics
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    • v.1 no.2
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    • pp.90-94
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    • 2017
  • Visible light identification (VLID) is a user identification system for a door lock application using smartphone that adopts visible light communication (VLC) technology with the objective of high security, small form factor, and cost effectiveness. The user is verified by the identification application program of a smartphone via fingerprint recognition or password entry. If the authentication succeeds, the corresponding encoded visible light signals are transmitted by a light emitting diode (LED) camera flash. Then, only a small size and low cost photodiode as an outdoor interface converts the light signal to the digital data along with a comparator, and runs the authentication process, and releases the lock. VLID can utilize powerful state-of-the-art hardware and software of smartphones. Furthermore, the door lock system is allowed to be easily upgraded with advanced technologies without its modification and replacement. It can be upgraded by just update the software of smartphone application or replacing the smartphone with the latest one. Additionally, wireless connection between a smartphone and a smart home hub is established automatically via Bluetooth for updating the password and controlling the home devices. In this paper, we demonstrate a prototype VLID door lock system that is built up with LEGO blocks, a photodiode, a comparator circuit, Bluetooth module, and FPGA board.

Design and Implementation of VLID System by Back-Scattering Visible Light (가시광의 후방산란을 이용한 VLID 시스템 설계 및 구현)

  • Yun, Jisu;Jang, Byung-Jun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.1
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    • pp.10-18
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    • 2017
  • In this paper, we designed and implemented a visible light identification(VLID) system consisting of a VLID reader and a tag which backscatters incident lights from the reader. A VLID tag sends its ID to the reader by switching an LCD shutter which is located on its surface. The VLID reader consists of six LEDs and a photodiode(PD). The LEDs emit visible light and a PD located in a center position of LEDs receives backscattered light from the VLID tag. A microcontroller and a commercial liquid crystal display(LCD) shutter for 3D-TV glasses are used to implement a VLID tag. Experiments were conducted to confirm VLID system performance. We successfully demonstrated experiments to send NRZ-OOK signal of 100 bps over a distance of 35 cm at daytime. Also, we suggested the theoretical maximum transmission rate and the various methods to enhance the separation distance between a VLID reader and a tag.

A Passive Visible Light Transponder Using an LED for an Optical Transceiver (LED를 광송수신 소자로 사용한 수동형 가시광 트랜스폰더)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.24 no.4
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    • pp.232-238
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    • 2015
  • In this paper, we introduce a passive transponder in which an LED is used for both a light transmitter and a receiver, and a solar cell is used for supplying power to the all devices in the transponder. The LED in the transponder operates as a photodetector in the receiving mode, and acts as a light source in the transmitting mode. The current responsivity of the LED detector was measured to be in the order of $10^{-4}A/W$, and the receiving bandwidth with a load resistance of $10k{\Omega}$ was about 10 to 30 kHz. Using the LED for an optical transceiver in a VLID transponder, the detection range was about 70 cm when the transponder was illuminated by the visible light from a $3{\times}3$ LED array in a reader.