How to compare the stability of lighting products?

The basic concept of flicker, flicker and the significance of luminous stability.

LED lighting products with many traditional lighting products can not match the advantages, of course, also has its inherent shortcomings or controversy. Among them, the strobe is one of the important arguments. In this paper, through the measurement and analysis of the luminous flux of various traditional lighting and LED lighting products, we give an indirect conclusion on whether there is the degree of strobe and strobe. Some suggestions are put forward for the design and application of the products.

The basic concept of flicker, flicker and the significance of luminous stability

The flash of LED lighting products has become the second most serious doubt following the blue light hazard controversy (many of the early questions that have been reached by industry efforts). For the existence of LED lighting strobe, the existence or extent of which circuit structure principle, and compared with the traditional lighting, there is no systematic analysis of the experimental report. Some people use digital camera, mobile phone of LED lighting products to take photos or videos, found some people for the measurement of interference fringes; Luo Tuo also found a stroboscopic flash, the LED lighting products for high-profile qualitative serious, not suitable for general lighting strobe. However, these experiments have to go deep analysis of digital image refresh rate? What is the speed of strobe? These parameters are the key parameters to determine whether someone can feel the strobe Digital camera can be seen as a high frequency of digital cameras and refresh the light frequency of high frequency beat strobe, which may not be able to feel the high frequency of the human eye, which is for people, there is no flash. Similarly, the problem can also be the speed of the screw. Therefore, it is of great practical significance to promote the lighting energy saving and emission reduction through the analysis of the problems in other experiments, to dispel people's doubts and to promote the healthy development of LED lighting.

How to compare the stability of lighting products?

The concept and principle of strobe and flicker

Blinking is usually a single light flashes or time intervals of the law of multiple light flashes, and the strobe is usually a regular interval of repeated changes in light. Any regular repetition of the light changes are produced by stroboscopic, and can be divided into people can feel the low-frequency flicker and people can not feel the high frequency strobe. Critical flicker and eye "persistence of vision" effect is closely related to the time. It may vary from person to person, and the same person may not be the same in different age, environment and time. When people observe the scene, the light signal into the brain, need to go through a short period of time. The end of the action of light, the previous scene will not immediately disappear, this phenomenon is called "persistence of vision". According to reports, the "fast moving objects, when the human eye to see the image of the object disappears, the human eye can still continue to retain the image of the object 0.1 to 0.4 seconds for the middle image; the brightness of the light stimulus, 'persistence of vision' time is about 0.05 to 0.2S". Without this effect, the human eye will see the constantly changing light, which is harmful to the physical and mental health. "Persistence of vision" make the eye of flicker sensitivity is greatly reduced, for example, people see the movie screen is comfortable for gradient. Is it because the film is 24 images per second (two picture between the interval of 0.042 seconds shorter than most people of the "persistence of vision" time). If there is no "human persistence", even if the studio is still landscapepainting, we will also see 24 images per second flashing picture, for some time to watch will cause headache.

Second, if the picture changes the time interval longer than the "persistence of vision" time, such as the early films were 8 pictures per second (two seconds longer than the interval between the 0.125 picture, part of the "persistence of vision", so the brightness before time) a picture in the brain when the persistence of declining, retained the "persistence of vision" time after going down to a certain extent (that completely disappeared) and then, the second picture is yet to come, this time in the brain or eyes is "dark", from "light" to "dark"; when the second picture brightness comes, is from the "dark" to "bright flashing"; the whole process is constantly "bright dark bright".

Third, also with the speed of the object. In a film of 8 frames per second, even the slow pace of walking, some people also seem to beat, discontinuous picture, the result is equivalent to the strobe. For now 24 pictures per second movie, walking speed has become a gradual change, but if it is a person or thing very fast movement makes the following second images of picture content and difference before a large, still there will be a serious strobe. Therefore, some TV, computer monitors, such as the need for a long time with the eye has been using 85Hz or 100Hz, such as higher refresh frequency, so that the display is very stable. People do not consciously direct viewing light, flicker, flicker or fluctuation is illuminated by lights people observe objects on the surface brightness change feeling phenomenon, and optical parameters of the lamp itself such as luminous flux, luminance, etc. only indirectly related to its fluctuation depth parameter.

According to the theory, absolutely no stroboscopic is stable DC working lamp. According to previous experience, the depth of light fluctuations (that is, the difference between the amplitude and the wave trough and the ratio of amplitude) is not more than 5% of the absolute no stroboscopic. The depth of the incandescent lamp is about 20% ~ 25%, the vast majority of people feel that there is no stroboscopic, but not absolutely no stroboscopic. Although a lot of ordinary lighting electric light source (lamp) in the normal 50Hz power supply when the volatility of the use of more than incandescent light, some reach 60% ~ 70%, or even 100%.

However, according to the pure current waveform, the same fluorescent lamp 20 ~ 50KHz high frequency electronic ballast fluorescent lamp as a sinusoidal current waveform and the inductance ballast of the approximate 50Hz current waveform of square wave fluctuations in the proportion, but people feel high frequency fluorescent light output is very stable, and even that is "absolutely" no flicker, this is the afterglow time of rare earth energy-saving lamps compared to high frequency wave cycle is much longer, to play the role of the light induced by smoothing.