• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.406-412
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• 2023

In this paper, we studied the effect of noise caused by ambient light on a reflective PPG measurement device using infrared light. Noise caused by ambient light was examined by dividing it into general situations and special situations. In the general situation, noise due to changes in time and ambient light sources was randomly observed, and in the special situation, a halogen lamp was used to observe the effect of noise variations. In the experiment, PPG signals were measured and data acquired in real-time depending on each situation, and the measured data was analyzed in the time domain and frequency domain. First, through a general situation experiments, it was visually observed that noise increases with the brightness of ambient light, and through frequency analysis, it was observed that the noise sources were white noise, power line noise, and internal noise of the circuit. Futhermore, using a halogen lamp, we experimented with the change in noise depending on the change in distance from the ambient light and calculated the SNR. As a result of the experiment, an SNR of 3.2 dB was shown at a distance of 50 cm with an irradiance of 278.3 W/m². It was observed that normal measurement was difficult at SNRs below that, and an irradiance of 27.7 W/m² was obtained. It showed a value of 18.2 dB at a distance of 2 m, and it was observed that normal PPG measurement was possible through a filter at values above that.

• Journal of Biomedical Engineering Research
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• v.35 no.5
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• pp.125-131
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• 2014

The purpose of this study is to verify the utility of reflected photoplethysmography sensor using two green light emitting diodes that influenced by ambient light. Recently it has been studied that green light emitting diode is suitable for light source of reflected photoplethysmography sensor at low temperature and high temperature. Another study showed that, green light is better for monitoring heart rate during motion than led light. However, it has a bad characteristic about ambient light noise. To verify the utility of reflected photoplethysmography sensor using green light emitting diode, this study measures the photoplethysmography signal that is distorted by ambient light and will propose a solution. This study has two parts of research method. One is measurement system that composed sensor and board. The sensor is made up PE-foam and Non-woven fabric for flexible sensor. The photoplethysmography signal is measured by measurement board that composed high-pass filter, low-pass filter and amplifier. Ambient light source is light bulb and white light emitting diode that has three steps brightness. Photoplethysmography signal is measured with lead II electrocardiography signal at the same time and it is measured at the finger and radial artery for 1 minute, 1000 Hz sampling rate. The lead II electrocardiography signal is a standard signal for heart rate and photoplethysmography signal that measured at the finger is a standard signal for waveform. The test is repeated 3 times using three sensor. The data is processed by MATLAB to verify the utility by comparing the correlation coefficient score and heart rate. The photoplethysmography sensor using two green light emitting diodes is shown better utility than using one green light emitting diode and red light emitting diode at the ambient light. The waveform and heart rate that measured by two green light emitting diodes are more identical than others. The amount of electricity used is less than red light emitting diode and error peak detectability factor is the lowest.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2062-2064
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• 2015

In this paper, we propose indoor positioning algorithm performed at the image sensor equipped in mobile station, which receives the light signal from LED panels. To evaluate the performance of positioning algorithm, we consider the ambient noise existing indoor environment, and it is found that the proposed algorithm estimates the position of mobile station with high accuracy regardless of existence of ambient noise.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.459-465
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• 2014

Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.411-414
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• 2000

Optical Triangulation Probes (OTPs) are widely used for their simple structure. high resolution, and long operating range. However, errors originating from speckle, inclination of the object, source power fluctuation, ambient light, and noise of the detector limit their usability. In this paper, we propose new design criteria for an error-reduced OTP. The light source module for the system consists of an incoherent light source and a multimode optical fiber for eliminating speckle and shaping a Gaussian beam Intensity profile. A diffuse-reflective white copy paper, which is attached to the object, makes the light intensity distribution on the change-coupled device(CCD). Since the peak positions of the intensity distribution are not related to the various error sources, a sub-pixel resolution signal processing algorithm that can detect the peak position makes it possible to construct an error-reduced OTP system

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.10-13
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• 2009

We have developed variety of LCD technologies for the out-door display, which improve out-door readability as well as reliability from external impacts. This improvement was made possible by new approach on LCD cell optical design and modification of LCD surface, which allows surrounding light to be transmitted to enhance the visibility and at the same time filtering out light, which are considered to be source of noise in terms of visibility. This technology enables users to maintain high display performance in both in-door & out-door environments moreover alternatively choosing in-door/out-door.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.1
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• pp.83-90
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• 2019

LED lighting is spreading on the strength of LED lighting, and various government policies are being implemented. VLC research which is a wireless communication technology using lighting has been actively conducted, and it has been proven through many studies that a general LED light source such as a high-speed data transmitter can be used. But from now on, one of the main problems is the noise from side lights, which can be compared to the noise of radio broadcasts. So in this paper, we proposed a noise canceling model to remove the interference of ambient light by using an optical filter for a detachable VLC channel. In order to verify the proposed model, various high brightness RGB LED modules were used for comparative analysis. In addition, the applicability was verified through experiments using High Luminance LED lighting which is applied in real life.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.595-601
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• 2015

These days, research related to Intelligent Transportation System (ITS) technology is being widely considered. ITS is inevitable for future transportation systems to reduce accidents, congestion, and offer a smooth flow of traffic. The use of Visible Light Communication (VLC) in ITS systems has been considered widely because of its EMC/EMI free and LED infrastructure reusable properties. Among the VLC schemes, this study analyzed the performance of the Color Shift Keying (CSK) scheme under a Vehicle-to-Infrastructure (V2I) downlink scenario to verify the capability of CSK as a communication tool for ITS. By modeling daylight noise using the modified Blackbody radiation model, this study examined the performance of V2I VLC under daytime conditions. The relationship between BER, the communication distance, and the amount of ambient-light noises under the pre-described V2I scenario were determined by simulations.

• Archives of design research
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• v.16 no.3
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• pp.381-390
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• 2003

The purpose of this study was to examine satisfactory of users and actual condition in the postpartum care center. This study focused on the private room for postpartum mothers. Data were collected through questionnaire survey including observations and interviews. The subjects of this subjects study were 240 postpartom mothers. The interviews were carried out from March 8th. 2003. to March 29nd. 2003 The data were analyzed by using SPSS-Win. The major results of this study were as follows: 1) The ambient elements such as noise, ventilation, and natural light should be considered primarily for the postpartum mother rooms. 2) The functional elements such as the size of the room, window, toliet are important factor of the satisfaction for users

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.404-407
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• 2008

Because of directly receiving the thing in which a microwave is reflected and comparing the frequency, the microwave sensor with doppler effect completely overcomes the problem of the passive infrared sensor. The microwave sensor with doppler effect well operates about a temperature, the dust, and the peripheral noise because of being dull in the most of ambient conditions. The system developed in this research is the electricity saving detection sensor which it senses the real time action of a man as the microwave sensor and automatically turns on the electric lamp and turns off, minimizes the electrical energy consumption. Since the microwave sensor is not influenced in the light, the dust, and the natural element like the ambient temperature, the effectiveness is considered to be superior to the passive infrared sensor being used currently. There was the energy reduction effect more than about 60% in the performed example which established this system. When this was compared with the construction cost, the cost of establishing payback period was about 1-1.5 year. The microwave sensor with doppler effect developed from this research result is convinced in the future to do enough for the electric energy saving.