LED purification lamps can often be used in indoor ligh […]
LED purification lamps can often be used in indoor lighting fixtures, and LEDs are used as light-emitting components. They are widely used in supermarkets, pharmaceutical factories, office offices, etc. Another important indicator of flat LED panel lamps is the uniformity of their light emission.
Another important indicator of LED flat light is its uniformity of light emission. The common standard GT004-2012 “LED flat luminaires for general indoor lighting” put forward the requirement of brightness uniformity, which refers to the minimum brightness and brightness on the light emitting surface of the luminaire. The ratio of the arithmetic mean.
As an LED flat lamp, the unevenness of light emission will cause the brightness of the panel display to be uneven and cause discomfort to the human eye. According to the requirements of the GT004-2012 standard, the brightness uniformity of LED flat lamps should not be less than 0.8. The test method is mainly based on the size of the screen, select the appropriate test points, and measure the brightness value of each point.
LED panel lamps with square side length L, rectangular long side L and circle diameter D not greater than 20cm shall be arranged as shown in the figure (a); LED panel lamps greater than 20cm shall be arranged as shown in the figure (b). The diameter of the test spot on the light emitting surface of the LED flat lamp is 2cm ~ 3cm. The brightness value of each point is subtracted from the average brightness to obtain the maximum value, and then the maximum value is divided by the average brightness and the percentage is the brightness uniformity. It is generally believed that the uniform performance of more than 80% has little effect on human perception.
The brightness uniformity test for flat lamps is the first time in the standard that the surface brightness of indoor lamps is required. It reflects the characteristic parameters of flat lamps and is one of the important characteristics of this type of lamps. In indoor lighting, surface-emitting lamps create soft and simple lighting effects that other bracket lamps or grille lamps cannot replace.
In indoor lighting, fluorescent lamps with diffuser plates also have a surface luminous effect. They have been used for many years, but they can not reach the level of brightness uniformity of LED flat lamps. The reason is that the fluorescent tube is an omnidirectional light source, the optical system can no longer be adjusted to achieve better brightness uniformity, and the efficiency of the lamp is 40lm / W. The light source of LED lamps is half-space. In the lamp, the light utilization rate is high, the lamp efficiency can reach more than 80lm / W, and the brightness uniformity can reach a higher level.
Using the side light guide structure LED flat lamp, the LED light emitting tube is arranged on the side of the light guide plate, and the visual effect of the lamp is better. At present, most domestic manufacturers still use printed light guide plates as light guide components, making use of various dense, diffusive points of various sizes to make the light guide plate emit light uniformly to obtain good light uniformity.
From the test results, the uniformity of the brightness of small-size LED panel lamps is easy to meet the requirements, and even if the uniformity is a bit off, it is not easy for the human eye to feel it. Large-area LED flat lamps sometimes have non-uniformity in brightness due to the quality of the light guide plate, and due to process reasons, the above-mentioned bright light band at the light entrance, or local dark areas can be seen. Therefore, the selection of the main raw materials such as light guide plates, diffusers, and reflective papers must be well evaluated, and the raw materials must be strictly controlled when entering the factory. The production enterprises should be equipped with the necessary optical brightness meters and light transmittance testing instruments.