A, what is a stroboscopic
Stroboscopic refers to the luminous flux of electric light source at a certain frequency fluctuations. Using a mobile phone on light can often find stripe distribution, which is caused by the stroboscopic. Some degree of stroboscopic won't pay attention, there is no physical discomfort; But some stroboscopic is really a problem. In the early 1990 s, there is a lot of research found that light stroboscopic and migraine headache, neurological diseases such as autism, visual fatigue and discomfort, there is a close relationship, serious can cause illusion, make the eye causing accidents. Don't look down upon stroboscopic, the influence of different frequency and volatility of depth to the person is not the same!
1. The visible stroboscopic
The human eye is a very complicated system, individual difference is very big, for the vast majority of people, can detect the light flashing, 80 hz at this time of the human eye can perceive light and shade change, flicker frequency at 80 hz, also known as the visible stroboscopic (visible flickr). Visible stroboscopic general lighting or display is unacceptable.
2. The stroboscopic effect
For more than 80 hz frequency flash, the human eye is not easy to find, but it has a great influence on space perception of the human eye. Such as moving object as a series of still images, namely the Stroboscopic effect (Stroboscopic effect). Because the stroboscopic effect, people will produce an illusion, and put some quick operation of the equipment as a slow running even still can be very dangerous.
Stroboscopic effect brought by machine illusion
3. The phenomenon of the phantom
Similarly, when light flicker frequency at 80 hz - 2 KHZ, and environment in the static object, the human eye in the mobile position or direction, static light spot, but there will be a system known as the phantom phenomenon, such as car tail lights, or scanning outdoor LED display, etc.
4. The dangers of stroboscopic
Light stroboscopic and migraine headache, autism, eye fatigue, blurred vision and other neurological diseases have a close relationship. Research shows that a 3-70 hz low frequency flashing light source for some people may cause photosensitive epilepsy; About 100 hz flicker frequency is considered can lead to headaches, migraine, For the 120 hz frequency flickering light source may affect the person's mood, appear boredom, anxiety, etc. The stroboscopic effect and related visual illusion resulted from the mechanical movement of step in industrial sites is very dangerous. Therefore, for the characteristics of stroboscopic lighting products accurate measurement and evaluation is directly related to people's health problems, need to be addressed.
Second, why the LED strobe
Turn LED lighting products adopt AC DC constant voltage or constant current power driver, do not produce stroboscopic light source itself, with or without stroboscopic depends on LED drive power supply due to drive differ in thousands ways, each LED products stroboscopic performance is different also. Especially some manufacturers in order to save costs, using a relatively simple drive circuit, such as AC leds, larger stroboscopic problems.
For the intelligent lighting products, light is its essential function, and the dimming is another cause of stroboscopic. And when the product loading the dimming function, stroboscopic tend to worsen. Especially in light is dark, the wave depth is larger, as shown in the figure below. So for dimming function, or declared dimming controller can connect lighting products, should be in its respectively in the dimmer and dimmer the brightest darker when measuring the stroboscopic performance.
Third, the stroboscopic evaluation standard
At present, there are multiple international, standardized research group on the in-depth research on stroboscopic subject, and it has been or is published standards or specifications, mainly include the following categories:
1. The energy star and IEEE
North American energy star product certification standard is the earliest stroboscopic to requirements for lighting products, one of the standard, in fact, as early as 2000 the IESNA lighting has been in the manual of stroboscopic clear definition and requirements are put forward.
2015 IEEE file, stroboscopic risk can be divided into several levels, as shown in the figure below, the level of green area coverage is risk free, while the yellow area is low risk classes, more than the yellow part is not acceptable.
2. State laws and regulations
In 2015 a California CEC regulations issued by the measurement and evaluation methods of stroboscopic put forward different requirements, the requirements in 40 hz and 90 hz and 200 hz and 400 hz and 1000 hz cutoff wave conditions, calculate percentage modulation, in general is more complicated.
3. The IEC standard
IEC covered light flicker frequency of 0.05 Hz - 80 Hz. Standards adopted in a short time flicker value Pst to evaluate visible stroboscopic. Simulates the human eye to intensity of illumination fluctuations in the calculation of the subjective visual feeling, through the instantaneous flicker visual sensitivity classification probability calculation, this flicker severity assessments for a set period of time. Limit for Pst = 1, when the Pst > 1, more than 50% of the observers feel stroboscopic.
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