The purchase of eye protection lamps depends on the shading performance of the lamps

Experts said that stroboscopic is not classified as an indicator of eye protection lamps, and the national standard 'shading performance' is the key to 'eye protection'. Stroboscopic table lamp index requirements' eye protection lamp 'concept has a long history, many businesses are' high-frequency flash ', 'no stroboscopic' and other words to indicate that their lamps not only do not 'hurt the eye ', more to protect eyesight, and even' prevent myopia '. In recent years, there are businesses that say their lamps are 'DC power supply ', which is healthier than the past' AC power supply lamps'. Is this really the case? Yang Zheng introduced that 'DC power supply' if it is clear that the current of the lamp works in pure DC mode, the light emitted by its light source will also be in DC form (superimposed on the basis of DC with small fluctuations or pulsations), from the perspective of physical domination, the volatility of its light is indeed much lower than the fluctuation of the light source of AC current work. At present, the table lamp using the LED light source module belongs to this type, but the input power supply is still in the form of AC. However, Yang Zheng explained that in fact, 'the sensitivity of the human eye to light volatility is in the low frequency range ', such as the frequency of warning lights such as ambulances is about 8-10 Hertz, which is most likely to cause discomfort to the human eye and cause everyone to be alert. These frequencies are much lower than the light frequency range of the normal AC power supply working light source, so 'there is no normal eye in the current civilian power supply frequency of the light source has an uncomfortable situation'. For example, he said that the light frequency of the most widely used light sources in the world is 50 to 60 Hertz. Since there is no low-frequency eye injury, there is no high-frequency eye protection. In addition, the reporter looked up the national standard "reading and writing desk lamp performance requirements", as' suitable for reading and writing lighting places similar to home, classroom and other places to use the table lamp 'national standard, the standard does not mention the so-called stroboscopic problem. According to the master reporter, in the opinion draft of the standard, the preface has mentioned that 'at present, high frequency flicker (flicker greater than the fusion frequency) affects the work of visual research results can not be sure that the response of the retinal nerve caused by high frequency light stimulation will affect any sensory or motor nerve visual function, so this standard does not include flicker in the technical requirements of the lamp'. Two factors determine whether the so-called 'eye protection lamp' is mostly ordinary desk lamps. The reporter learned that the national standard "reading and writing desk lamp performance requirements" made provisions on the table lamp from the project indicators related to the eyes, such as: specifies the color characteristics of the light source and color rendering index requirements (5.7.2), noise requirements (5.10) and so on. The standard also specifies the light shading requirements of the lamp (5.8.1, that is, 'the eye distance from the height of the reading desk 400mm, the horizontal distance from the light source 600mm to look at the lamp, should not see the reflector wall and the light source'). Yang Zheng explained that the luminous surface can not be projected onto the retina of the human eye, which is the real eye protection requirements of the lamp. Another item related to 'eye protection' is the 'illuminance requirement '(5.8.2, this standard requires that the lamp on the desktop lighting should be more uniform, and the lighting area should cover the area of reading and writing operations, otherwise it is easy to cause visual fatigue.)