Flicker Effects Research Articles

Digital implementations for determination of temporal light artefacts of LED luminaires

Flicker and stroboscopic effects caused by a temporally modulated light source may be harmful for the human visual system. Standardized measurement methods have been developed for the related temporal light artefacts of LED luminaires. It was found out that the performance of the International Electrotechnical Commission (IEC) recommended flickermeter implementation is highly dependent on sampling frequency. Novel digital implementations for the flickermeter and stroboscopic effect visibility measure (SVM) were created to remove any inaccuracies. The performance of the novel Aalto implementations does not depend on the sampling frequency when running the test waveforms of the IEC standard through the implementations. As compared with the IEC recommended digital implementations, Aalto flickermeter decreases the average error related to the test waveforms from −0.05 to +0.003, and Aalto SVM meter also decreases the average error by almost two orders of magnitude.

Methods to Reduce Flicker and Light Pollution of Low-Mounting-Height Luminaires in Urban Road Lighting

Current low-mounting-height luminaires (LMHLs) have low effective luminous flux, high surface brightness, and many stray lights, resulting in high energy consumption and light interference, and the flicker effect may threaten driver safety. Currently, the flicker effect in LMHL lighting has been relatively poorly studied. However, in prior research, a Flicker Index (FI) quantification model was developed. In this study, we have modified the FI model to incorporate visual persistence, visual masking, and driving speed of the driver, and proposed a dynamic energy ratio model for quantifying flicker effects. The notion of effective luminous flux in road lighting was introduced, revealing that the reasons for high energy consumption, severe light pollution, and strong flicker effects in regular LMHLs were low effective luminous flux and high surface brightness. We recommend a low-mounting-height lighting technique that functions in both forward and reverse directions, which can significantly enhance the effective luminous flux of lighting fixtures, reducing stray light. The lighting fixtures created were tested on a road. The findings suggest that the energy consumption of both forward and reverse lighting fixtures is only 40% of the international standard requirements, resulting in 81% more energy savings than in existing LMHLs. The surface brightness of forward and reverse lighting fixtures is only 1.18 cd/m2, which is equivalent to 0.001% of the surface brightness of existing lighting fixtures. This indicates that 99.89% less invalid light is projected into the environment, indirectly reducing light pollution. Additionally, the flicker index of these fixtures is only 2% of that of existing lighting fixtures, reducing the impact of the flicker effect on drivers. This study provides insights into quantifying and mitigating the flicker effect in LMHLs, as well as presenting novel approaches and strategies for enhancing the efficiency and reducing light pollution of streetlamps.

Effects of flicker with various brightness contrasts on visual fatigue in road lighting using fixed low-mounting-height luminaires

The flicker effect caused by the periodical succession of bright and dark bands on the road surface and tunnel walls can momentarily distract drivers and poses a safety concern. Low-mounting-height luminaires are typically used to illuminate long underground roads. However, the resulting flicker effects persist for longer duration, which can cause accidents. Although flicker frequencies have been extensively discussed, limited studies have focused on the effect of the ratio of background brightness to luminaire surface brightness on the flicker effect in road lighting. In this study, two experiments were performed to investigate the effect of reducing brightness contrast (BC) on human visual fatigue. BC can be decreased by reducing the surface brightness of the lamp (Experiment 1) and increasing background brightness (Experiment 2). The flicker frequencies in Experiment 1 were 4 and 6 Hz, and 6 Hz in Experiment 2. The study involved 49 participants. The results revealed that the blink rate and visual fatigue change rate (VFCR) decreased with a decrease in BC. The flicker frequency of 6 Hz is more effective than that of 4 Hz by reducing the surface brightness of lamps on the VFCR. This method is more effective in reducing the brightness of the surface of the lamp than increasing the background brightness to relieve eye fatigue. The proportion of time in a minute that the eyes are at least 80% closed (P80) increases as BC increases. This study may provide guidance for urban road lighting and road lighting product design.

Flicker: A review of temporal light modulation stimulus, responses, and measures

Flicker has been an important lighting system consideration for over a century. More precise terms are temporal light modulation (TLM) as the stimulus, and responses to TLM as the unwanted visual, cognitive, or physiological consequences. As lighting technology evolved, different forms of TLM emerged, and so did responses to them. Today, some LED systems – encompassing the LED, driver, and control – can result in TLM causing severe unwanted effects, while other LED systems produce no unwanted effects at all. LED systems can deliver a much wider range of luminous waveforms than conventional lighting systems, some exhibiting very high modulation depths. More than any light source before, they can elicit perceptions of the phantom array. Direct flicker effects at modulation frequencies less than about 80 Hz and the stroboscopic effect at frequencies greater than 80 Hz are fairly well understood, but the phantom array effect needs more exploration and characterisation. This review focuses on the technology and research history that led to current metrics for quantifying TLM and human responses to TLM. Visually impaired individuals may exhibit alterations in their response to TLM, but such a discussion is beyond the intent of this review. Thus, the focus is on individuals with normal visual function.

Flicker elimination in grids with distributed generation using group predictive voltage and frequency regulators

In this work, we determine the control efficiency of grids with distributed generation and the possibility of eliminating flicker therein using group predictive voltage and frequency regulators. A small-size thermal power plant with the transformer connection to a power grid and consisting of three turbogenerators with a capacity of 2.5 MV·A each and a voltage of 6 kV was considered as a distributed generation plant. An isolated power supply system with three 2.5 MV·A gas turbine units each operating on static and motor loads was also considered. Automation control methods were used. Studies were conducted in the MatLab environment using the Simulink and SimPowerSystems simulation packages. The obtained results demonstrate that, upon temporarily activating the power load in the point of connecting a distributed generation unit and using inconsistent regulators, fluctuations occurring in the rotor speed and turbogenerator voltage indicate the presence of flicker effects. A similar situation can be caused by a sudden change in the forecast time for individual predictive speed controllers. Following the disconnection of a 0.4 s short circuit, a voltage flicker was found to occur in the vicinity of the gas turbine plant. However, local or group predictive regulators allow the problem of flicker emergence to be solved. The use of group predictive regulators allows flicker to be eliminated more effectively: the transient time is reduced by 1.7 and 2.7 times for the generator rotor speed and voltage, respectively. Moreover, for voltage, over-regulation is practically eliminated. The conducted computer simulation confirmed that flicker can be eliminated by applying group control of turbine generators using predictive speed controllers. Similarly, for a grid with gas turbine units, the use of predictive control algorithms made it possible to eliminate flicker without solving the problem of adjusting regulators. At the same time, group predictive regulators eliminate flicker more effectively, thereby improving the quality indicators of the control process.

Research into the Effect of Photometric Flicker Event on the Perception of Office Workers

Today the number of office workers has reached to an enormous number due to the fast-growing technology. Most of these office workers spend long hours in enclosed spaces with little/no daylight penetration. The lack of daylight causes physiological and psychological problems with the workers. At this point lighting systems become prominent as the source and the solution of the problem. Photometric flicker event which arises in the lighting systems can sometimes become visible and brings a lot of issues with it. In this paper, an experimental work has been done to investigate the effect of flicker. For this purpose, the flicker values of 3 different experiment rooms for different lighting conditions and scenarios have been measured and a questionnaire study has been carried out in the experiment rooms with 30 participants. In conclusion, the effect of the flicker event on the volunteers have been classified and some methods have been proposed not to experience flicker effects.

New flickermeter sensitive to high‐frequency interharmonics and robust to fundamental frequency deviations of the power system

In this study, a new flickermeter sensitive to high-frequency interharmonics and robust to fundamental frequency variations is proposed, implemented and tested. The standard IEC flickermeter, proposed in the 61000-4-15 IEC Standard, considers only the interharmonics around the fundamental frequency and ignores the effect of high-frequency interharmonics on the voltage peak fluctuation. However, high-frequency interharmonics have been shown to have significant effect on the flicker in the literature. This work combines the effect of both low- and high-frequency interharmonics on flicker, based on a voltage-peak-detection flickermeter algorithm. Using a spectral correction procedure applied during the flicker computation, the proposed flickermeter becomes also robust to fundamental frequency variations existing in power systems. The accuracy of the proposed flickermeter has been tested and proved by synthetic voltage data including fundamental frequency variations, harmonics and interharmonics around the fundamental as well as those at higher frequencies. The results obtained with field data obtained from electricity transmission network changes as whether considering flicker effects of high-frequency interharmonics or not. In high-frequency mode, including the effect of high-frequency interharmonics, the proposed method yields higher flicker values compared to the IEC flickermeter. In low-frequency mode, excluding them, both IEC flickermeter and the proposed flickermeter yield close flicker.

Individual Alpha Peak Frequency Predicts 10 Hz Flicker Effects on Selective Attention.

Rhythmic visual stimulation ("flicker") is primarily used to "tag" processing of low-level visual and high-level cognitive phenomena. However, preliminary evidence suggests that flicker may also entrain endogenous brain oscillations, thereby modulating cognitive processes supported by those brain rhythms. Here we tested the interaction between 10 Hz flicker and endogenous alpha-band (∼10 Hz) oscillations during a selective visuospatial attention task. We recorded EEG from human participants (both genders) while they performed a modified Eriksen flanker task in which distractors and targets flickered within (10 Hz) or outside (7.5 or 15 Hz) the alpha band. By using a combination of EEG source separation, time-frequency, and single-trial linear mixed-effects modeling, we demonstrate that 10 Hz flicker interfered with stimulus processing more on incongruent than congruent trials (high vs low selective attention demands). Crucially, the effect of 10 Hz flicker on task performance was predicted by the distance between 10 Hz and individual alpha peak frequency (estimated during the task). Finally, the flicker effect on task performance was more strongly predicted by EEG flicker responses during stimulus processing than during preparation for the upcoming stimulus, suggesting that 10 Hz flicker interfered more with reactive than proactive selective attention. These findings are consistent with our hypothesis that visual flicker entrained endogenous alpha-band networks, which in turn impaired task performance. Our findings also provide novel evidence for frequency-dependent exogenous modulation of cognition that is determined by the correspondence between the exogenous flicker frequency and the endogenous brain rhythms.SIGNIFICANCE STATEMENT Here we provide novel evidence that the interaction between exogenous rhythmic visual stimulation and endogenous brain rhythms can have frequency-specific behavioral effects. We show that alpha-band (10 Hz) flicker impairs stimulus processing in a selective attention task when the stimulus flicker rate matches individual alpha peak frequency. The effect of sensory flicker on task performance was stronger when selective attention demands were high, and was stronger during stimulus processing and response selection compared with the prestimulus anticipatory period. These findings provide novel evidence that frequency-specific sensory flicker affects online attentional processing, and also demonstrate that the correspondence between exogenous and endogenous rhythms is an overlooked prerequisite when testing for frequency-specific cognitive effects of flicker.

Designing Static VAr Compensator capacity to enhance power quality in electric arc furnaces

This paper introduces a method for reducing damages arising from voltage fluctuations, voltage flicker, imbalance in the three-phase and power factor reduction caused by electric arc furnaces. A novel equation is defined to calculate the susceptance values of the static var compensator control system, the active power functions of phase load as well as the reactive power ones that have been used to suppress the voltage fluctuation. By compensating the impulsive part of active power component in the impulsive loads, not only can we reduce voltage fluctuations, flicker effects, balance the system and increase the power factor, but also voltage stabilization can be directly controlled. By studying this method and simulating on Electro-Magnetic Transients Program (EMTP) software, we can see that, according to the allowable flicker limit, a compensation method can balance the system, increase power factor and resolve the problem of voltage fluctuations and flicker.

조명의 디밍을 지원하는 이진 가시광 통신에 대한 플리커의 주파수 분석

This paper presents an impact of flicker for various binary modulations of visible light communication (VLC) under dimming requirement. While previous approaches consider the statistics of the signal that cannot capture contributions of dynamic impacts of flicker, the power spectral density is evaluated for various VLC transmission schemes of dimming support. This enables to compare transmission schemes with the contribution of low and intermediate frequency components to flicker. Numerical results show that analog dimming has advantages over other techniques in terms of flicker and signal processing with waveforms and symbol distribution allows to mitigate flicker effects.

Robust flicker evaluation method for low power adaptive dimming LCDs

Abstract This paper describes a robust dimming flicker evaluation method of adaptive dimming algorithms for low power liquid crystal displays (LCDs). While the previous methods use sum of square difference (SSD) values without excluding the image sequence information, the proposed modified SSD (mSSD) values are obtained only with the dimming flicker effects by making use of differential images. The proposed scheme is verified for eight dimming configurations of two dimming level selection methods and four temporal filters over three test videos. Furthermore, a new figure of merit is introduced to cover the dimming flicker as well as image qualities and power consumption.

Disco, Cybernetics, and the Migration of Warhol’s <em>Shadows</em> into Computation

[A]nd now we have a band, the Velvet Underground, who will belong to the biggest discotheque in the world, where painting and music and sculpture can be combined and that's what I'm doing now. . . .-Andy Warhol, Warhol: My True Story (I960)1Now you have art, video art, late night art.-Andy Warhol, Q & A: Andy (1985)2[CJomputer graphics provide the logical space of which any given perspective painting forms a more or less rich subset.-Friedrich Kittler, Computer Graphics (2001)3The image comes to us from an essentially symbolic creation, that is from a machine, that most modern of machines, far more dangerous than the atom bomb, the adding machine.-Jacques Lacan, The Circuit (1988)4The medium is extremely forgetful.-Niklas Luhmann, The Medium of the Art (1990)5Disco as MediumAndy Warhol's Shadows, a series of 102 paintings that Warhol completed in 1978 and first exhibited in 1979, is notable for marrying an abstract, somber serial painting sequence to a somewhat incongruous popular cultural format: disco. Warhol said, Someone asked me if they were art and I said no. You see, the opening party had disco. I guess that makes them disco decor.6 Given the offhandedness of Warhol's remark, it is not surprising that little commentary has been directed to the work's links to technical media-notably strobe lighting, the cathode ray tube (CRT), and computing technologies-media that would prove instrumental in the expansion of what Warhol called nightclub art, video art, late night art. In spite of Warhol's stated desire to be like a machine, little attention has been directed to the connections between the Shadows' imagery distribution patterns and a species of machine-based imagery grounded in what Benjamin Buchloh has termed an emerging aesthetics of information administration and delivery.7 This essay examines two favored Warholian devices-strobe and CRT-whose flicker effects bear the hallmarks of a new media system and its attendant logic-coupled to the slower, analog, and antecedent medium of painting that Warhol was, not surprisingly, and after Marcel Duchamp, tethered to in various stages of abandonment. Such medial devices had two main consequences: they facilitated the infusion of digital or ur-digital imagery into painting, thus aligning painting with postwar developments in information theory, and they supplied Warhol with an updated, machine-based logic of image production with which to recalibrate the New York avant-garde art scene along specific medial lines.Executed in 1978, Shadows ushers from a technological order radically different from Warhol's earlier photo silk screens. In referencing the mathematically precise generation of imagery achieved by measured voltage passing through a strobe lamp as well as the compositing of an image along horizontal and vertical axes that marks the raster scan in TV's CRT, Shadows embodies a new media logic, one instrumental in revising Warhol's earlier claim to want to be, and presumably paint, like a machine: The reason I'm painting this way is that I want to be a machine, and I feel that whatever I do and do machine-like is what I want to do.8 Like Warhol's 1960s' work, grounded in newspaper halftone photos, Shadows is no less about platform-specific modes of data transmission. In particular, the Shadows' closest medial precursor remains the Exploding Plastic Inevitable (EPI), which marshaled film, television, music, and strobe to create an expanded-scale, intermedia environment. As Branden Joseph notes, the EPI's variable strobes, spots, pistol lights, mirror balls, and loudspeakers engendered an intermedial, electric space,9 one singled out by Marshall McLuhan for its utopie, participatory dimensions, but which participants typically found aggressive, chaotic, visceral, and dissonant. A mere eleven years separates EPI from Shadows, but the differences are telling. …

Elimination of harmonic induced viable bifurcations with TCSC for ac–fed electric arc furnaces

AC-fed electric arc furnaces (EAFs) are known with their unbalanced, excessively nonlinear and time varying load characteristics. The nonlinear oscillations produced by EAF operation cause several problems to interconnected feed system. Injection of harmonics/interharmonics and rising flicker effects on the feed system are two of major problems produced by EAF. These nonlinear effects result into quasistatic changes in the feed system parameters (L − R) . In last decade many studies have been reported that such quasistatic changes in the feed system parameters result in viable bifurcation formations which strictly cause sudden and drastic changes on system behaviors. This paper presents an analytical control procedure to eliminate viable bifurcation points on L − I and R − I curves that cause sudden resonant peak arc currents. After control procedure, stability margins of EAF are extended into larger levels and viable bifurcation points on the feed system parameter have been eliminated. During study, possible roles of small parameter changes of uncontrolled EAF around bifurcation points and controlled EAF have been traced over time series analysis, phase plane analysis and bifurcation diagrams. A wide collection of useful dynamic analysis procedures for the exploration of studied arc furnace dynamics have been handled through the AUTO open-source algorithms.

Materiality and Meaning in Recent Projection Performance

The Velvet Light Trap, Number 70, Fall 2012 DOI: 10.7560/VLT7003 ©2012 by the University of Texas Press, PO Box 7819, Austin, TX 78713-7819 nyone paying attention to experimental cinema in the past fifteen years or so will have noticed that an aesthetic of materiality and medium specificity has returned. Despite (perhaps even because of) the everdecreasing availability of analog film brought about by digital media, film’s unique properties and possibilities have become the central subjects of experimental cinema to an extent not seen since the 1960s and 1970s. This development is particularly evident in the spate of films produced using nontraditional production methods that leave visible traces of themselves in the finished work, thereby reflexively calling a viewer’s attention to film’s distinct physical properties. These methods tend to involve a more direct, tactile involvement with film stock on the part of the maker, hence an increasing number of handmade films—films scratched, drawn upon, sewn, punctured, buried in earth, covered with foreign objects, and hand-processed using unpredictable alternative chemicals and methods. Also predominant are flicker effects, filmstrips displayed as objects, worked-over found footage, and “mistakes” arising from the contingencies of mechanical filmmaking at such a grass-roots, artisanal level—flares, chemical burns, and inconsistencies of color and exposure caused by hand-processing. All these features signal a renewed obsession with the stuff of analog, “celluloid” film and a celebration of its special qualities.1 But if medium specificity is back with a vengeance, it is also back with a difference. This difference—the nature of contemporary manifestations of medium specificity in experimental cinema—is what I shall explore here. As a case study, I will examine recent film projection performance, which involves the live manipulation of film projectors. The use of film projection in live performance can be traced back to the first generation of European modernists, including the surrealists and the artists afMateriality and Meaning in Recent Projection Performance jonaThan waLLey

Individual differences in vulnerability to subjective time distortion1

Time duration is perceived to be longer when accompanied by dynamic sensory stimulation than when accompanied by static stimulation. This distortion of time perception is thought to be due to the acceleration of an internal pacemaker that has been assumed to be the main component of temporal judgments. In order to investigate whether the function of the internal pacemaker is modality dependent or independent, we examined the correlation of visual flicker and auditory flutter effects on a temporal production task. While seeing a 10-Hz visual flicker or hearing a 10-Hz auditory flutter, participants estimated a duration of 2500 ms as accurately as possible by pressing a button. The results showed a significant within-individual correlation between the time distortion due to visual flicker and that due to auditory flutter. Additionally, we found that time distortion due to auditory flutter tended to be larger in female participants than in male participants. These results suggest that the mechanisms underlying subjective time dilation are similar between vision and audition within individuals, but that they vary across individuals.

Effects of flicker characteristics from solid-state lighting on detection, acceptability and comfort

A study to assess the detection and acceptability of flicker and stroboscopic effects under different lighting conditions was conducted. Frequencies from 50 Hz to 300 Hz were assessed, as well as different modulation amounts, duty cycles, waveform shapes and correlated colour temperatures. For the range of conditions evaluated, direct perception of flicker was negligible at 100 Hz or higher, but stroboscopic effects could be perceived at 300 Hz. Reducing flicker modulation from 100% to 33% decreased perception of stroboscopic effects. A higher duty cycle was associated with slightly lower discomfort. The implications for solid-state lighting systems producing high-modulation flicker are discussed.

Analysis of the Effects of Flicker on the Blood-Flow Variation in the Human Eye

Flicker annoyance measurement, regardless if it is performed by processing the supplying voltage or by evaluating the light emitted by the lamp, relies on the assumption of a proper model of the behavior of the complex eye-brain system in the presence of fluctuating light. The only experimental data available are the ones obtained, for a certain incandescent lamp, by asking several people to report their perception about the flicker to which they were subjected. In this paper, the possibility of achieving an ldquoobjectiverdquo evaluation of the flicker effects on a human subject is investigated. In particular, the increment of the blood flow in a vessel at the optic nerve is considered and taken as a possible index of annoyance due to flicker.

Influence of Wind-Energy-Converter Control Methods on the Output Frequency Components

This paper analyzes the influence of different wind-energy-converter control methods on the connected electrical grid. As the wind energy propagates through the converter to the mains, their frequency components are influenced by the conversion processes. The plant control strategies have a major influence on these components. In particular, frequencies between 2 and 8 Hz can cause undesired flicker effects in the connected grid. For the grid stability, it is beneficial to dampen these frequency components in the power output. The influences of the control methods on these frequency components are analyzed in this paper.

Limits for Interharmonics in the 1–100-Hz Range Based on Lamp Flicker Considerations

At present, limits do not exist for harmonics that are non-integer multiples of the power frequency. Any limit developed must 1) be based on some level above which undesirable consequences appear, 2) be measurable by some defined and defensible method, and 3) be as simple as possible. In this paper, limits for non-integer harmonics, here called interharmonics, are developed based on the light flicker effects that such components may cause. Once limiting values are determined based on light flicker using the flickermeter protocol defined by the International Electrotechnical Commission (IEC), they are assessed relative to other physical phenomena, such as overheating, which form the basis for existing integer harmonic limits such as those proposed by the IEC and the Institute for Electrical and Electronics Engineers. The ultimate contribution of this paper is a limit curve for frequencies 0-100 Hz (for 60 Hz systems) that fulfills the three criteria for a limit as previously defined

On the compensation of non‐active current components of three‐phase loads with quickly changing unsymmetry

AbstractSome types of loads, like arc furnaces, present a special challenge to compensation strategies. They vary quickly and have a very high rated power. For example the arcs of an arc furnace are not burning continuously especially when starting the melting process. This causes variations of the line voltage with frequencies well below the line frequency commonly known as voltage flicker. Because of cost efficiency the energy storage capability of compensators for the mitigation of voltage flicker effects can still only be small compared to the energy taken by the arc furnace during one period of the line voltage. This paper discusses the use of a compensation tool which quickly detects negative sequence current components in comparison to the calculation of an equivalent conductance using the so‐called FBD method (Fryze‐Buchholz‐Depenbrock method). Simulations are used to demonstrate the advantages and disadvantages of the tool for detecting negative sequence current components. It is shown that the quick detection and compensation of negative sequence current components can reduce the amount of voltage flicker considerably.