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Good uniformity

LED panel light is another important indicator of its luminous uniformity, the two sides common standard GT004-2012 “indoor general lighting with LED flat panel lamps” put forward the brightness uniformity (luminanceuniformity) requirements, refers to the light emitting surface of the minimum brightness and brightness The arithmetic mean ratio.

As the LED panel light, the non-uniformity of the light will result in the uniform brightness of the panel display, causing the human eye to feel uncomfortable. In accordance with the requirements of the GT004-2012 standard, LED flat panel luminaire brightness uniformity should not be less than 0.8. The test method is mainly based on the size of the screen size, select the appropriate test point, measured the brightness value of each point.

The length of the side of the square L, the long side of the rectangle L and the circular diameter D is not more than 20cm of LED flat lamps, according to the requirements of (a) the requirements of distribution; LED flat lamps greater than 20cm layout requirements (b). In the LED flat light emitting surface of the test spot diameter of 2cm ~ 3cm, the brightness of each point after subtracting the average brightness and take the maximum value, and then divided by the maximum average brightness percentage is the brightness uniformity. Generally believed that the average performance of more than 80% of the human eye has little effect on the perception.

Flatness Luminaire brightness uniformity test is the first time in the standard requirements of indoor luminaires surface brightness. It reflects the characteristics of flat panel lighting parameters, is one of the important features of this type of lighting. In interior lighting, surface lighting to create a soft and simple lighting effect is that other stent lamps or grille lamps can not be replaced.

Indoor lighting, fluorescent lamps with diffuser plate also has a surface light effect, has been used for many years, but not up to the level of uniformity of LED flat panel lamps brightness. The reason is that the fluorescent tube is omnidirectional light source, can no longer adjust the optical system to achieve better brightness uniformity, and lamp performance is 40lm / W level. The LED lamps light source is half space light, in the lamp, light utilization, lighting efficiency can reach more than 80lm / W, while the brightness uniformity can reach a higher level.

The use of side light guide structure LED panel light, LED LED is arranged in the side of the light guide plate, the visual effect of lighting is better. At present, most domestic manufacturers still adopt a printed light guide plate as a light guide component, and utilize various diffusion points of different sizes and sizes to make the light guide plate emit light uniformly to obtain good light uniformity.

From the test results, the small size LED flat panel lamp brightness uniformity easily meet the requirements, even if a little deviation from uniformity, the human eye is not easy to feel it. Larger area LED flat panel light, sometimes due to the quality of the light guide plate brightness unevenness, as well as the process causes light above the light zone, or visible local dark area phenomenon. Therefore, the light guide plate, diffuser, reflective paper and other major raw material selection to make a good quality evaluation, and strict control of raw materials into the plant, the production enterprises should be equipped with the necessary optical brightness meter and light transmittance test equipment.

4, color difference

From the human eye’s visual sensitivity, people are sensitive to the yellow and green colors, meaning that the two colors are slightly fluctuating and can be felt by the human eye. The same production enterprises to produce LED panel light, different batches of products should not exist obvious color, or users in the product after the failure is difficult to re-buy the same color products.

The standard stipulates that the light color of three LED panel lamps should be consistent at random. The difference of the average color coordinate CIE1976 (u’v ‘) of the three samples should not exceed 0.004. At the end of the luminous flux maintenance test, the deviation of the chromaticity of the LED panel luminaire from the initial value should be within 0.007 of the CIE 1976 (u’v ‘) diagram.

In the LED flat lamp lamps, commonly used colors are red, green, blue and white, the unit of measurement of color is nm (nano), for color sensitive people, as long as the color is a little bit fluctuating can feel. To control the color, we must control the raw materials. In order to avoid the differences caused by the different color wavelengths, lighting production companies should control the LED light source.

Such as the green wavelength of 525-530nm, separated by 5nm, yellow 580-585nm, separated by 5nm. The red can be 620-628nm, separated by 8nm, green wavelengths can be more than 5nm above can feel that even if less than 8nm red will not be too obvious. However, to reduce color, to avoid some of the uncertainties caused by long-term use, such as color drift, the same color wavelength control within 2nm is appropriate. Therefore, the control of the color index is often important, because different people are not the same color recognition.

For white light, it is usually marked with color temperature, warm white is generally 3000-3500K, white 3500-5000K, cold white 5000K-6500K. General packaging manufacturers LED color temperature separated by 500K, there are 1000K apart, the error of the color temperature within the package factory requirements are generally plus or minus 200K. Therefore, should choose a stable color LED light source, the production process must be strictly controlled.

Detecting color LED Panel found that the selection of three different flat lamp test sample, products of different manufacturers are not the same color, there will be a gap, some LED panel light color product than the standard requirements, mainly through analysis the reason is that the manufacturer could not performed when the LED light source carefully selecting effective screening, each LED optical performance is not good consistency, resulting in different emission color different flat lamp, visual perception difference between the large area of ​​the mounting, there gives Uncomfortable feeling

To improve this common problem, one is to make supplier evaluation, choose a relatively fixed manufacturer; the second is to LED product suppliers to provide product consistency requirements to ensure continuity of supply and a variety of performance indicators are relatively consistent and stable; Third, companies should also strengthen their own LED inventory inspection, excluding color difference exceeds the required LED, to ensure that the LED flat panel produced consistent with the requirements.

5, there is a problem

At present, the performance of LED devices is constantly improving, and its application range is also growing. LED dimmable products are also constantly innovating, and application areas are constantly expanding. The continuous improvement of the efficiency of high-brightness white LEDs has led to the demand for contra-lateral LED panel lamps, which in turn has promoted the research and development of new LED panel lamps, resulting in the continuous emergence of new side-panel LED panel lamps.

However, LED panel light there are some problems.

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First, the lamp performance, for side-entry LED flat panel light, low efficiency is still an urgent issue to be solved. On the one hand, to achieve high brightness, you must increase the number of chips to increase power, but the energy-saving effect of poor performance, especially large-size flat-panel lamp; the other hand, increased power, lighting equipment, LED module operating temperature will increase, Affecting light failure and life expectancy, so how to choose a high light efficiency LED light source needs to be considered, the current commercial LED luminous efficiency has more than 130lm / W.

Second, the light fades inconsistencies, LED flat-panel lamp due to the use of a larger number of LEDs, individual inconsistencies between the decline will not only reduce the brightness, on the other hand may also lead to uneven LED flat lamp the probability of increase, if Is the use of RGB color LED flat panel light, different colors of LED light failure is also different, the possibility of greater heterogeneity. Let the LED work below the rated power, sacrificing a certain efficiency, is a better solution, as far as possible to reduce the light fades.

The third is the discreteness of LED device parameters, based on the LED flat panel lamp brightness color rendering requirements, LED panel lamp work, under constant voltage source conditions, the current of each LED device should be consistent, constant current source work, the voltage should Consistent, while the brightness and wavelength of each LED should also be consistent. Therefore, the same LED panel LED used to be filtered, in particular, luminous efficiency, luminous flux, the main wavelength, color temperature and pressure drop and other indicators should be within a certain margin of error.

Fourth, the price, based on the LED application of some special requirements on the flat panel lamp, multiple parameters should be basically the same, so that enterprises for the LED flat panel lamp LED devices, the production process to be strictly controlled, sorting, an increase of production enterprises Manufacturing costs, in the near future to replace the traditional grid lights do not have the price advantage. Although there are still some technical problems that need to be solved as mentioned above, it is believed that the LED panel light will surely be an area of ​​continuous improvement and new product innovation.

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