Light Waveforms Research Articles

Analysis of Photoplethysmographic Waveform for Assessment of Pulpal Blood Flow in Children

본 연구는 ë§¥ë°•ì‚°ì†Œì¸¡ì •ê¸°ë¥¼ 이용하여 ê´‘ìš©ì ë§¥íŒŒ 파형의 원데이터를 ê¸°ë¡í•˜ê³ ë¶„ì„í•¨ìœ¼ë¡œì¨ 치수 ìƒí™œë ¥ ì¸¡ì •ì— 이 원데이터 분석의 ì ìš©ê°€ëŠ¥ì„±ì„ ì‚´íŽ´ë³´ê³ ì •ìƒ 치수 ìƒí™œë ¥ì„ 갖는 소아환자의 ìƒì• ì¤‘ì ˆì¹˜ì— 대한 ê´‘ìš©ì ë§¥íŒŒ 파형의 파라미터에 대한 기초 자료를 ë§ˆë ¨í• ëª©ì ìœ¼ë¡œ 시행되었다.ìƒì• ì¤‘ì ˆì¹˜ì— 대해 ì •ìƒ 치수 ìƒí™œë ¥ì„ ê°–ê³ ì „ì‹ ì§ˆí™˜ì´ 없는 30ëª ì˜ 환아(남 16ëª , 여 14ëª , í‰ê· ì—°ë ¹ 11.4세)를 연구대상으로 ì„ ì •í•˜ì˜€ë‹¤. 맞춤형 센서와 ë§¥ë°•ì‚°ì†Œì¸¡ì •ê¸°ë¥¼ 이용하여 ì¸¡ì •í•˜ì˜€ìœ¼ë©° ì¸¡ì •ê²°ê³¼ëŠ” ì ìƒ‰ 파장과 ì ì™¸ì„ íŒŒìž¥ì˜ 원데이터 형태로 ê¸°ë¡ë˜ì—ˆê³ LabChart(v.7.3, ADInstruments, Germany)를 이용하여 분석하였다.본 연구를 통해 소아에서 ì •ìƒ ì¹˜ìˆ˜ìƒí™œë ¥ì„ 갖는 ìƒì• ì¤‘ì ˆì¹˜ì— 대한 ê´‘ìš©ì ë§¥íŒŒ 파형의 파라미터의 기준값을 ì œì‹œí• ìˆ˜ 있었으며 소아의 ì¹˜ìˆ˜í˜ˆë¥˜ì¸¡ì •ì— 이러한 ê´‘ìš©ì ë§¥íŒŒ 파형 분석이 í™œìš©ë ìˆ˜ 있음을 확인하였다.

基于积分球的高功率激光多参数测量技术

Aiming at the disadvantage that the traditional measurement technique is sensitive to the incident direction of incident light, a beam-split technique of high power laser multi-parameter measurement based on integrating sphere is proposed. Numerical analysis and simulation about attenuation rate, time waveform of emergent light, and time waveform recovery of incident light are carried out by Monte-Carlo method, which validate the feasibility that the integrating sphere can be used as beam-splitter in laser measurement system. The energy and time waveform of nanosecond laser is measured based on integrating sphere. The theoretical analysis matches well with the experiment result. Experiment and simulation results show that spectrum parameter, energy parameter and time parameter of incident light can be recovered by measuring the parameters of the emergent light, when the light-split technique is used in laser parameters measurement. The proposed technique can conquer the disadvantage that the incident direction of incident light has great influence on the parameters of the emergent light in traditional technique. The proposed technical proposal possesses small volume and is easy to integrate, which can be used in modular design of multiple beam high power laser parameters measurement system.

Partial discharges triggered by metal-particle on insulator surface under standard oscillating impulses in SF<sub>6</sub> gas

The characteristics of partial discharge (PD) triggered by a metal particle on an insulator’s surface were studied experimentally under standard oscillating lightning impulse (OLI) and standard oscillating switching impulse (OSI) conditions. Light emission detection was carried out to assist in PD measurement. Experiments showed that the largest number of successive PDs occurred during the rise time of each oscillation period of applied impulses and that a small number of reversed-polarity PDs occurred during the fall time. The composition of the PD sequence was determined by the position of the particle on the insulator’s surface. Specifically, when a needle particle detached from the plate electrodes, the PD sequences consisted of both negative point PDs and positive point PDs. Two types of negative discharge, three types of positive discharge, and reversed-polarity discharge were differentiated by their current and light pulse waveforms. In these experiments, detectable partial discharge inception voltages (PDIVs) of the three particle positions were investigated at gas pressures from 0.05 to 0.35 MPa. The light emission inception voltages (LEIVs) were lower than PDIVs under OLI, OSI, and AC voltages. These inception voltages of different particle positions could be sorted as follows: LEIV < PDIV+ (d = 30 mm) < PDIV- (d = 0 mm) < PDIV+/- (d = 15 mm). We demonstrated that the OLI voltages could excite PDs from defects at lower equivalent voltage levels than for OSI and a 50 Hz AC voltage, and the PDs under OLI were more active in terms of occurrence frequency than those under OSI and AC voltages. A simple model was proposed to explain PD inception and propagation under oscillating impulses. The rapid change of background electric field and the formation and accumulation of charges on the insulator’s surface were considered the main causes of the greater efficiencies of OLI and OSI at exciting PDs compared with the AC voltage.

Address Discharge Simulation of Additional Pulse Application to Common Electrode in AC PDP

The address discharge simulation and the light waveform are investigated when the additional pulses are applied to the common electrode during an address period in AC plasma display panel. The wall charges in a cell are accumulated on three electrodes during a reset period and those are utilized to produce the address discharge triggering in addition to the externally applied voltage between the scan and address electrodes during an address period. As the accumulated wall charges should be utilized on the overall electrodes to improve the address discharge triggering, the additional pulses are applied to the common sustain electrodes when the scan and address pulses are driven. In this study, the Xe 3P2 energy state to generate the vacuum ultraviolet are simulated when the scan and address pulses on two electrode are applied including the additional pulses on the common electrodes. In addition, the address discharge light waveforms in the conventional and the proposed driving method are measured and compared.

Coupled thermal-optic effects and electrical modulation mechanism of birefringence crystal with Gaussian laser incidence**Project supported by the National Natural Science Foundation of China (Grant No. 51176039).

We study the Gaussian laser transmission in lithium niobate crystal (LiNbO3) by using the finite element method to solve the electromagnetic field’s frequency domain equation and energy equation. The heat generated is identified by calculating the transmission loss of the electromagnetic wave in the birefringence crystal, and the calculated value of the heat generated is substituted into the energy equation. The electromagnetic wave’s energy losses induced by its multiple refractions and reflections along with the resulting physical property changes of the lithium niobate crystal are considered. Influences of ambient temperature and heat transfer coefficient on refraction and walk-off angles of O-ray and E-ray in the cases of different incident powers and crystal thicknesses are analyzed. The E-ray electrical modulation instances, in which the polarized light waveform is adjusted to the rated condition via an applied electrical field in the cases of different ambient temperatures and heat transfer coefficients, are provided to conclude that there is a correlation between ambient temperature and applied electrical field intensity and a correlation between surface heat transfer coefficient and applied electrical field intensity. The applicable electrical modulation ranges without crystal breakdown are proposed. The study shows that the electrical field-adjustable heat transfer coefficient range becomes narrow as the incident power decreases and wide as the crystal thickness increases. In addition, it is pointed out that controlling the ambient temperature is easier than controlling the heat transfer coefficient. The results of the present study can be used as a quantitative theoretical basis for removing the adverse effects induced by thermal deposition due to linear laser absorption in the crystal, such as depolarization or wave front distortion, and indicate the feasibility of adjusting the refractive index in the window area by changing the heat transfer boundary conditions in a wide-spectrum laser.

FPGA-based chlorophyll fluorescence measurement system with arbitrary light stimulation waveform using direct digital synthesis

Nowadays, it is critical to generate technology to be applied to crops in order to counteract the lack of food, which can be produced by several biotic and abiotic factors. It is well known that stress conditions affect photosynthetic activity, which is closely related to crop yields. As a result, chlorophyll fluorescence can be used as an appropriate analytical tool to investigate the physiology and stress conditions of photosynthetic organisms, and to improve them. This paper presents an FPGA-based measurement system with direct digital synthesis capabilities for Chlorophyll fluorescence measurement. This is achieved through a customizable waveform processor that is capable of implementing arbitrary waveforms to modulate light source, get new frequency components to enrich information that a photosynthetic sample can generate, and provide researchers with new ways to obtain physiological information.

All-optical ternary signal processing using uniform nonlinear chalcogenide fiber Bragg gratings

The fiber Bragg grating (FBG) has a huge capacity in optical communication, especially for showing optical multistability, which can be used in optical switching and optical memories. In this paper, we numerically solve the coupled mode equations governing the uniform FBG and obtain the output shapes of the bright and dark solitons as input pulses with different amplitudes. This paper shows that we can reach different output shapes using identical input shapes with different amplitudes. Hence we can control the output light waveform using light as the controlling input. For signal processing purposes, it is made clear that the input pulse characteristics, such as amplitude and shape, are distinguishable applying only the output shape. Also, we can predict the length of the FBG. The deliverables of this article will facilitate generating light pulses with application to optical fiber digital communication systems.

A flicker perception metric

A metric is proposed for predicting the perception of light source flicker from a measurement of the relative light output waveform. The metric is the weighted quadrature sum of the temporal spectral components comprising the waveform after dividing by the waveform mean. The metric’s foundation is that used by the IEC flickermeter, which assumes a linear, time invariant human response to flicker. This assumption, restated in terms of the spectral components being additive and independent, was found to accurately model the flicker detection thresholds for a range of waveform shapes and frequencies. In the testing of the additive and independence requirements, the empirical spectral sensitivity to flicker was measured for 10 observers. The metric also correctly predicted whether flicker was detected for five commercial A-lamps.

Simultaneous Multichannel Waveform Recovery of Illumination Signals Using Compressed Sensing

A critical element of any time-of-flight (ToF) 3D imaging system is the illumination. Most commercial solutions are restricted to short range indoor operation and use simple illumination setups of single or few LEDs, grouped together. Recent developments toward medium and long range ToF imaging, ready for outdoor operation, bring the need for powerful illumination setups, constituted by many emitters, which might be grouped in distributed modules. Provided that the depth accuracy of ToF cameras strongly depends on the quality of the illumination waveform, assuring that a complex illumination system is providing a homogeneous in-phase wavefront is of capital importance to minimize systematic inaccuracies. In this letter, we present a novel framework for multichannel simultaneous testing of illumination waveforms, which is able to recover the waveform of the incident light on each pixel of a ToF camera, exploiting the sparsity of typical continuous wave illumination signals in frequency domain.

High Voltage Sensing Based on Fiber Fabry–Perot Interferometer Driven by Electric Field Forces

Based on the mechanism of the liquid flow caused by charged particles and dielectrophoresis under electric field-induced forces, an optical fiber Fabry–Perot interferometer for measuring high voltage is proposed and demonstrated. A second-order equation is established to express the relationship between the voltage signal and the output light signal. In our experiment, both sinusoidal signal with 7 kV, 50 Hz, and instantaneous pulse signal with dozens of kilovolts are employed as testing voltage sources. The results show that when the pulse voltage is applied, the output light signal exhibits a waveform near to the impulse response of a second-order system. A formula is derived to reveal the feature of linear and quadratic voltage effects in the experiment. As for ac voltage response of 50 Hz, the output light waveforms show only ∼0.1 ms delay. There is a good agreement between the theory and the experimental result. Moreover, there is no need to use expensive materials and polarization devices in the scheme. Our proposed sensing technique has the potential to measure high pulse voltage or the periodic high voltage.

Energy-Efficient Brightness Control and Data Transmission for Visible Light Communication

This letter considers the efficient utilization of energy in a visible light communication (VLC) system. A joint brightness control and data transmission are presented to reduce the total power consumption while satisfying lighting and communication requirements. An optimization problem is formulated to determine the optimal parameters for the input waveform of light emitting diode (LED) lamps; this problem reduces the total energy consumption of the LED lamps while ensuring the desired brightness and communication link quality. The simulation results show that the proposed scheme increases the energy efficiency of the VLC system.

Integrated Multichannel Electronics for High Performance Time Correlated Single Photon Counting

The analysis of extremely weak, ultrafast and periodical light signals is increasingly widespread in a large number of fields, from chemistry and biology to telemetry and communication, and in a great variety of applications, from quantum cryptography to fluorescence imaging.Speaking of fluorescent lifetime analysis, for example, the detection of very faint and fast optical signals is fundamental to investigate the complex interactions between molecules that play a key role in many crucial issues such as the origin and growth mechanisms of tumors. In this domain the Time-Correlated Single Photon Counting (TCSPC) technique is very effective to reconstruct the light waveform when both extremely high time resolution and linearity are required.TCSPC is based on the detection of single photons and on the record of their arrival times: if the probability of detecting a photon during one excitation cycle is far less than one, the histogram of photon arrivals per time bin exactly corresponds to the temporal trend of the light signal. In order to properly reconstruct the light waveform a time measurement block featuring very high performance is necessary: this circuit has to be able to measure time intervals of few hundreds of nanoseconds with picosecond time resolution and a differential non-linearity much lower than few percents of the time bin width.Moreover a growing number of techniques do now require to collect data from multiple channels at the same time. Förster Resonance Energy Transfer (FRET), Fluorescence Diffuse Optical Tomography (FDOT) and single-molecule spectroscopy, for example, can benefit a lot of a system capable of providing simultaneous analysis in temporal or spectral range. Indeed, concurrency not only reduces the measurement time, revealing dynamic phenomena even on very short timescales but it also opens the way to spectrally resolved measurements that analyze different events occurring simultaneously, like Fluorescence Cross-Correlation Spectroscopy (FCCS).Nevertheless the development of a truly parallel acquisition system featuring both high performance and a high number of independent channels is still an open challenge: to achieve this goal the design of a time measurement circuit capable of acquiring data from several channels in parallel while providing high performance on each channel is of the utmost importance. In this work a fully integrated array of 16 time to amplitude converters (TAC) designed in 0.35µm SiGe technology is presented.The first simulations show very high performance on each channel with a FWHM time resolution lower than 19ps and a differential non linearity lower than 0.4% peak-to-peak of the LSB. In order to reduce the overall area of the chip, pairs of converter stages share all the conversion chain through a 2 input multiplexer. The simulated dead time on the entire full scale range is 191ns, corresponding to a maximum conversion frequency of 5.24MHz per channel. The obtained results on the designed 16 channel TAC array are extremely good and, if the performance are verified by experimental measurements, this array will be one of the fundamental blocks of a fully parallel high-performance TCSPC acquisition system. Based on high efficiency fully custom single photon detectors (SPAD) and on a front-end electronics specifically designed to properly work with these sensors, the final system will be the upgrade of a few channels high performance acquisition chain already developed in the same technology.

OLED Electrical Equivalent Device for Driver Topology Design

In this paper, a hardware equivalent of an organic light-emitting diode (OLED) was designed and investigated. This substitution OLED device is based on a circuit-equivalent OLED model and can be used to design and test OLED dedicated drivers. Indeed, OLEDs are available on the market, but they are still very expensive and hard to obtain. Compared to a real OLED, the substitution device is cheap and robust and can be easily duplicated. Moreover, a photodetector is not required to measure the light output waveform. This can be simply done by measuring a voltage across a resistance. This model can be used, for instance, to simulate a large OLED panel made of several associated single OLEDs for various series/parallel connection strategies. It can also be used to simulate aging phenomena by changing the values of some of its components. This might be useful for the definition of strategies to compensate aging effects like luminous flux depreciation. Another advantage of such a device is its use for power supply tests as it could serve as a substitution load, at maximum deviation from standard OLED electrical characteristics. We discuss the theoretical model that was used as a basis for developing the device. The accuracy of the model was then evaluated, particularly in pulsewidth-modulation dimming conditions. Then, the hardware equivalent device was compared to a real OLED. Finally, an example of the potential use of this substitution device is given: It was successfully used to investigate the “overdrive” technique in order to increase OLED light output rise time. This technique improves the light output rise time by a factor of over 4.

任意波形脉冲泵浦下掺铒光纤的自发辐射

In order to study the active spontaneous emission of erbium-doped fiber pumped by arbitrary waveform pulse with breaking the limitation of pump waveform before.By dividing the time into tiny periods,the expressions for level population and the average power of active spontaneous emission were obtained with rate equations.Simulations and experiments show that pump glitches have less effect on the active spontaneous emission just like having a "high frequency filter";the waveforms of the pump light and active spontaneous emission light are alike when the pump power is large relatively,this research can be used to all-optical modulation for the optical fiber laser.The results are consistent with the theoretical analysis,which show the analysis is reliable.

Optical Measurement of Blood Oxygen Saturation of Dental Pulp

The applicability of arterial pulse oximetry to dental pulp was demonstrated using in vitro and in vivo measurements. First, porcine blood of known oxygen saturation (SO2) was circulated through extracted human upper incisors, while transmitted-light plethysmography was performed using three different visible wavelengths. From the light intensity waveforms measured in vitro, a parameter that is statistically correlated to SO2 was calculated using the pulsatile/nonpulsatile component ratios of two wavelengths for different SO2. Then, values were measured in vivo for living incisors, and the corresponding SO2 values were calculated using the results of in vitro measurements. The estimated SO2 values of the upper central incisors measured in vivo were from 71.0 to 92.7%. This study showed the potential to measure the oxygen saturation changes to identify the sign of pulpal inflammation.

Scalable time reversal of Raman echo quantum memory and quantum waveform conversion of light pulse

We have found a new hidden symmetry of time reversal light–atom interaction in the photon echo quantum memory with Raman atomic transition. The time-reversed quantum memory creates generalized conditions for the ideal compression/decompression of time duration of the input light pulses and its wavelength. Based on a general analytical approach to this scheme, we have studied the optimal conditions for the light field compression/decompression in resonant atomic systems characterized by realistic spectral properties. The demonstrated necessary conditions for the effective quantum conversion of the light waveform and wavelength are also discussed for various possible realizations of the quantum memory scheme. The performed study promises new capabilities for fundamental study of the light–atom interaction and deterministic quantum manipulation of the light field, significant for quantum communication and quantum computing.

Characteristics of the N2/O2 mixtures

The characteristics of the prebreakdown phenomena in low-pressure N2/O2 mixtures under quasi-dc uniform field gap were investigated. The appearance characteristics expressed schematically. The light, voltage and current waveforms of prebreakdown phenomena and the onset voltage of glow discharges were measured under conditions of 1/spl les/ pd/spl les/ 6 (Torr.cm) for N2/O2 mixtures. From these results it became clear that the forms of prebreakdown phenomena of the glow discharges observed under lowpressure N2/O2 mixtures were divided into four types, and these appearance characteristics were expressed schematically and discussed.

Four Channel, 40 ps Resolution, Fully Integrated Time-to-Amplitude Converter for Time-Resolved Photon Counting

Recently, a growing interest has arisen about the time-correlated single photon counting (TCSPC) technique, that allows the analysis of fast and weak light waveforms with a time resolution in the picosecond order. Since TCSPC basically consists of the measurement of the arrival time of a photon, a high resolution and high linearity time measurement block is of the utmost importance; moreover, the use of multianode Photo Multiplier Tube and of single photon avalanche diode arrays led to the development of multichannel acquisition systems, where the time measurement block has to be integrated to reduce both cost and area. We have designed and fabricated a four channel fully integrated time-to-amplitude converter (TAC), built in 0.35 μm Si-Ge technology, characterized by an excellent time resolution (less than 50 ps full width half maximum), low differential nonlinearity (better than 0.02 LSB peak-peak and 0.0003 LSB rms), high counting rate (16 MHz), low and constant power dissipation (50 mW) and low area occupation (2.58 × 1.28 mm2 ). Moreover, the very low crosstalk ( -115 dB) between channels, together with low power and low area makes the converter suitable for large scale multi-channel acquisition chains.

Secondary reverse streamer observed in an ester insulating liquid under negative impulse voltage

The so-called ‘secondary reverse streamer (SRS)’ in this study depicts a newly observed streamer-in-liquid phenomenon which subsequently occurs well after the extinction of the primary streamer (PS) propagation within a single shot of negative impulse voltage and has reverse polarity to the PS. Tests were carried out in a synthetic ester liquid at a 50 mm needle–plane gap under negative impulse voltages up to 140 kV. Based on the current and light waveforms as well as the photographic images, two types of SRS were found: one has a bright trunk with a high velocity of 9.79 km s−1 belonging to the 3rd mode streamer; and the other has a weak tree-like channel with a low velocity of 1.28 km s−1 resembling the 2nd mode streamer. It should be emphasized that SRS under negative impulse voltages has positive polarity being opposite to the negative PS, which is believed to be due to the reverse electric field induced by the residual space charges left by the PS. This has been confirmed by further verification tests under tail-chopped impulse voltages, for SRSs are significantly enhanced in both axial and lateral directions after the early removal of the external applied field.

DC breakdown characteristics in the gap with thin dielectric sheet in air

The dc breakdown characteristics in the gap with the thin dielectric sheet under atmospheric air were investigated experimentally. The breakdown phenomena were divided into three patterns by current and discharge light (photon) waveforms. The first pattern consisted of a single waveform as a primary pulse. The second pattern consisted of multiple secondary pulses as the successors of the primary pulse. The third pattern was a developing process from the second pattern to the breakdown of the sheet as a final stage. The breakdown voltage of the sheet was irregular even under the same experimental conditions, and its value increased with the sheet thickness. On the other hand, the breakdown voltage in the complex gap consisting of the thin sheet and air gap became higher than that of the thin sheet, and its maximum value reached the breakdown voltage in the air gap. These phenomena and the breakdown mechanism for each pattern were analyzed by the electric field distribution between the electrodes. The breakdown models in the gap with the thin sheet and the complex gap were proposed by comparing the experimental results with the breakdown mechanisms.