For nearly 30 years, LED technology has experienced a rapid development process. Because of its inherent advantages such as high efficiency, long life and low loss, vibration resistance and fast response speed, LED has been widely applied such as indicator light, display screen, traffic lights and so on, and it is currently being explored to be applied to lighting area.
Because China hasn’t established LED photometric standards, it has severely affected the improvement of LED quality and the unity of values and quantities, as well as the international trade and international technical communication about Led exchange and promotion. Therefore, in recent years the LED products in China has increased in quality and variety, but compared with foreign advanced countries, the gap is obvious.
In this situation, we set out to the LED measurement of optical parameters the meticulous research, and LED the establishment of national photometric standards.
2.1 Luminous Efficiency and Flux
The luminous efficiency is the ratio of the flux and power. The luminous efficiency represents the energy-saving characteristics of the light source, which is an important index to measure the performance of modern light source.
2.2 Luminous Intensity and Light Intensity Distribution
LED luminous intensity indicates its luminous intensity in a certain direction. Because LED intensity in different space angle is quite different, consequently we studied the light intensity distribution LED characteristics. This parameter has very big practical significance, and directly affects the minimum view of the LED display device. For example, if the LED large color displays in stadium has chosen the LED single pipe distribution of a narrow range, so viewers in the face of the larger screen angle will see the image distortion. The traffic signal lights also demands a bigger range of people to identify.
For the spectral characteristics of LED, we basically consider whether its monochromatic is fine, and also need to consider whether the main color of Led such as the red, yellow, blue, green, white and so on is pure. Because in many cases, for example the traffic lights has strict requirement for the color, however, now the colors of some of China’s LED signal lamp are observed to be green for blue, red for scarlet. From this phenomenon to see, it is very important and necessary for us to conduct the special study of the spectral characteristics of LED special study.