Abstract： This paper has introduced the basic concept of the flashing light source, the causes, and discussed all kinds of harm of the flashing light source and the flashing effect, stated the evaluation and measurement method of the flashing, finally measured the flash intensity of several typical light source. Thee data and the analysis result can be the reference of the health lighting.
Key words: flashing, stroboscopic effect, fluctuations depth, transient photometric
Basic concept of flashing
People will feel uncomfortable when reading under fluorescent lamp for a long time, even the radiance is different with the daytime. Why? After researches, we found that the light intensity of the fluorescent lamp is changing with the time. It is because of the flashing of the light source.
What is the light source flashing? The light source flashing is that the light emitted from the light source changes rapidly, which makes the light source beating and unstable. It is not easy for human eyes to be aware of the flashing of the light source. When in 8.8Hz, human eye is the most sensitive. At the same time, the maximum flashing frequency (critical flicker frequency) is changing with the intensity of the light source. With the increase of the light intensity, the critical flicker frequency is also increasing, when the light intensity increases to the maximum value, and then decreases gradually; the critical flashing frequency relatively decreases. When the light intensity is changing with the frequency of more than 50Hz, most people will not tell whether the light source is flashing or not. At this moment, the light source will emit a stable, continual light, because the reflection of the human eye did not catch up with the changing of the light source. For example, human eye will not be aware of the scintillation of the fluorescent lamp as 100 times each second (100Hz）.
The light flashing will be confirmed by stroboscopic effect. Sometimes, we may find such a phenomenon, when one object moves or rotates rapidly, it seems that their speed is slower than their actual speed, even when the object motion or the rotation frequency is the same with the light flashing frequency(or the integer times relationship), the object seems to be motionless. This is the reason of the causes of the flashing, it is a phenomenon that we do not except that to happen in the daily lighting. In fact, because of the flashing effect, people are easy to produce illusion. It is dangerous to regard the equipment of fast rotation as the slow rotation even stillness.
Light source flashing can be classified into the following types:
1. Periodic flashing: such as the flashing of the exchange fluorescent lamp and the light source flashing caused by the mains voltage fluctuation;
2. Aperiodic flashing: the start flashing of the exchange fluorescent lamp, all kinds of fault flashing;
3. Display equipment flashing: such as TV, computer, electronic game, the flashing caused by the advertising screen and other scanning Display;
4. Art lamp flashing: such as neon light, colored lamp and laser flashing.
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