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Temporal Light Effects
Temporal light effect (TLE) is the general term for all side-effects resulting from temporal light modulation (TLM). Root cause Light emitted from lighting equipment such as luminaires and lamps may vary in strength as function of time, either intentionally or unintentionally. Intentional light variations are applied amongst others for warning, signalling (e.g. traffic-light signalling, flashing aviation light signals), entertainment (like stage lighting), metrology (strobe light for measurement of rotation speed), navigation (like optical beacons, lighthouses) or for communication (Li-Fi). Generally, the light output of lighting equipment may also have unintentional light level modulations due to the lighting equipment itself. The magnitude, shape, periodicity and frequency of the TLM will depend on many factors such as the type of light source, the electrical mains-supply frequency, the driver or ballast technology and type of light regulation technology applied (e.g. pulse-wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Light Modulation
In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply ( power-line flicker) or incompatibility with an external dimmer. Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium. Flicker exists for other organisms having different perceptual thresholds. Light meters and image sensors can potentially detect flicker at much higher frequency bands than human vision. Shutter speeds used in motion photography can interact with high frequency flicker to produce visual artifacts in the captured imagery that betray flicker that would not otherwise be noted. The spectral sensitivity of the human eye to flicker depends upon the mode of visual perception. Due to the flicke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Queensway Tunnel
The Queensway Tunnel ( signposted as the Birkenhead Tunnel or B'head Tunnel) is a road tunnel under the River Mersey, in the north west of England, between Liverpool and Birkenhead. Locally, it is often referred to as the "old tunnel", to distinguish it from the newer Kingsway Tunnel (1971), which serves Wallasey and the M53 motorway traffic. At in length, it is the longest road tunnel in the UK. History Planning and construction The first tunnel under the River Mersey was for the Mersey Railway in 1886. The first tunnel crossing was proposed in 1825, and again in 1827. A report in 1830 rejected the road tunnel due to concerns about building damage. During the 1920s there were concerns about the long queues of cars and lorries at the Mersey Ferry terminal, so once royal assent to a parliamentary bill was received, construction of the first Mersey road tunnel started in 1925, to a design by consulting engineer Sir Basil Mott. Mott supervised the construction in association wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power-line Flicker
Power-line flicker is a visible change in brightness of a lamp due to rapid fluctuations in the voltage of the power supply. The voltage drop is generated over the source impedance of the grid by the changing load current of an equipment or facility. These fluctuations in time generate flicker. The effects can range from disturbance to epileptic attacks of photosensitive persons. Flicker may also affect sensitive electronic equipment such as television receivers or industrial processes relying on constant electrical power. Causes Flicker may be produced, for example, if a steel mill uses large electric motors or arc furnaces on a distribution network, or frequent starting of an elevator motor in an office building, or if a rural residence has a large water pump starting regularly on a long feeder system. The likelihood of flicker increases as the size of the changing load becomes larger with respect to the prospective short-circuit current available at the point of common conne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stroboscopic Effect
The stroboscopic effect is a visual optical phenomenon, phenomenon caused by aliasing that occurs when continuous rotational or other cyclic motion is represented by a series of short or instantaneous samples (as opposed to a continuous view) at a sampling rate close to the period of the motion. It accounts for the "wagon-wheel effect", so-called because in video, spoked wheels (such as on horse-drawn wagons) sometimes appear to be turning backwards. A strobe fountain, a stream of water droplets falling at regular intervals lit with a strobe light, is an example of the stroboscopic effect being applied to a cyclic motion that is not rotational. When viewed under normal light, this is a normal water fountain. When viewed under a strobe light with its frequency tuned to the rate at which the droplets fall, the droplets appear to be suspended in mid-air. Adjusting the strobe frequency can make the droplets seemingly move slowly up or down. Depending upon the frequency of illuminatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Light Interference
Temporal light interference (TLI) is an unacceptable degradation of the performance of an equipment or system that has an optical input for its intended functioning and is caused by a temporal light modulation disturbance. A temporal light modulation (TLM) disturbance may be either an intentional or unintentional temporal light modulation (TLM) of lighting equipment such as luminaires or lamps. Examples of equipment that can be interfered are barcode scanners, cameras and test equipment. NOTE – Temporal light modulations may also annoy human beings. In general, undesired effects in the visual perception of a human observer induced by light intensity fluctuations are called Temporal Light Artefacts (TLAs). Root causes of TLI Temporal light modulation disturbances may arise from fluctuations of the light intensity of lighting equipment. Light emitted from lighting equipment such as luminaires and lamps may vary in strength as function of time, either intentionally or unintentiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Light Artefacts
Temporal light artefacts (TLAs) are undesired effects in the visual perception of a human observer induced by temporal light modulations. Two well-known examples of such unwanted effects are '' flicker'' and ''stroboscopic effect''. Flicker is a directly visible light modulation at relatively low frequencies (80 Hz) and larger intensity variations. __TOC__ Relevance Various scientific committees have assessed the potential health, performance and safety-related aspects resulting from temporal light modulations. TLAs must be limited to certain levels to avoid annoyance due to the direct visibility by humans and to prevent potential health issues. After longer exposure, TLAs may reduce task performance and cause fatigue. Possible health effects for specific persons are photosensitive epileptic seizure, migraine and aggravation of autistic behavior. The incorrect perception of the motion of an object due to stroboscopic effect may be unacceptable in working environments with fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Light Interference
Temporal light interference (TLI) is an unacceptable degradation of the performance of an equipment or system that has an optical input for its intended functioning and is caused by a temporal light modulation disturbance. A temporal light modulation (TLM) disturbance may be either an intentional or unintentional temporal light modulation (TLM) of lighting equipment such as luminaires or lamps. Examples of equipment that can be interfered are barcode scanners, cameras and test equipment. NOTE – Temporal light modulations may also annoy human beings. In general, undesired effects in the visual perception of a human observer induced by light intensity fluctuations are called Temporal Light Artefacts (TLAs). Root causes of TLI Temporal light modulation disturbances may arise from fluctuations of the light intensity of lighting equipment. Light emitted from lighting equipment such as luminaires and lamps may vary in strength as function of time, either intentionally or unintentiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosensitive Epilepsy
Photosensitive epilepsy (PSE) is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns. PSE affects approximately one in 4,000 people (5% of those with epilepsy). Signs and symptoms People with PSE experience epileptiform seizures upon exposure to certain visual stimuli. The exact nature of the stimulus or stimuli that triggers the seizures varies from one patient to another, as does the nature and severity of the resulting seizures (ranging from brief absence seizures to full tonic–clonic seizures). Many PSE patients experience an " aura" or feel odd sensations before the seizure occurs, and this can serve as a warning to a patient to move away from the trigger stimulus. The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing lights (such as strobe lights) or rapidly changing or alternating images ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Light Artefacts
Temporal light artefacts (TLAs) are undesired effects in the visual perception of a human observer induced by temporal light modulations. Two well-known examples of such unwanted effects are '' flicker'' and ''stroboscopic effect''. Flicker is a directly visible light modulation at relatively low frequencies (80 Hz) and larger intensity variations. __TOC__ Relevance Various scientific committees have assessed the potential health, performance and safety-related aspects resulting from temporal light modulations. TLAs must be limited to certain levels to avoid annoyance due to the direct visibility by humans and to prevent potential health issues. After longer exposure, TLAs may reduce task performance and cause fatigue. Possible health effects for specific persons are photosensitive epileptic seizure, migraine and aggravation of autistic behavior. The incorrect perception of the motion of an object due to stroboscopic effect may be unacceptable in working environments with fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stroboscopic Effect
The stroboscopic effect is a visual optical phenomenon, phenomenon caused by aliasing that occurs when continuous rotational or other cyclic motion is represented by a series of short or instantaneous samples (as opposed to a continuous view) at a sampling rate close to the period of the motion. It accounts for the "wagon-wheel effect", so-called because in video, spoked wheels (such as on horse-drawn wagons) sometimes appear to be turning backwards. A strobe fountain, a stream of water droplets falling at regular intervals lit with a strobe light, is an example of the stroboscopic effect being applied to a cyclic motion that is not rotational. When viewed under normal light, this is a normal water fountain. When viewed under a strobe light with its frequency tuned to the rate at which the droplets fall, the droplets appear to be suspended in mid-air. Adjusting the strobe frequency can make the droplets seemingly move slowly up or down. Depending upon the frequency of illuminatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power-line Flicker
Power-line flicker is a visible change in brightness of a lamp due to rapid fluctuations in the voltage of the power supply. The voltage drop is generated over the source impedance of the grid by the changing load current of an equipment or facility. These fluctuations in time generate flicker. The effects can range from disturbance to epileptic attacks of photosensitive persons. Flicker may also affect sensitive electronic equipment such as television receivers or industrial processes relying on constant electrical power. Causes Flicker may be produced, for example, if a steel mill uses large electric motors or arc furnaces on a distribution network, or frequent starting of an elevator motor in an office building, or if a rural residence has a large water pump starting regularly on a long feeder system. The likelihood of flicker increases as the size of the changing load becomes larger with respect to the prospective short-circuit current available at the point of common conne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lighting
Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting (architecture), Daylighting (using windows, skylights, or Architectural light shelf, light shelves) is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants. Indoor lighting is usually accomplished using light fixtures, and is a key part of interior design. Lighting can also be an intrinsic component of landscaping, landscape projects. History With the Control of fire by early humans, discovery of fire, the earliest form of artificial lighting used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
