Light emitting diode (LED), referred to as LED for short, is a commonly used light emitting device. It emits light by combining electrons and holes. It is widely used in the lighting field. LED can efficiently convert electric energy into light energy, which has a wide range of applications in modern society, such as lighting, flat panel display, medical devices, etc.

This electronic component appeared as early as 1962. In the early stage, it could only emit red light with low luminosity. Later, other monochromatic versions were developed. The light that can be emitted has spread all over visible light, infrared light and ultraviolet light, and the luminosity has also been improved to a relatively high luminosity. It is also used as indicator light and display board at the beginning; With the continuous progress of technology, LED has been widely used in displays and lighting.

The important aspects of LED optical parameters are luminous flux, luminous efficiency, luminous intensity, luminous intensity distribution and wavelength.

Luminous efficiency and luminous flux

Luminous efficiency is the ratio of luminous flux to electric power, usually in lm/W. Luminous efficiency represents the energy-saving characteristics of light sources, which is an important indicator to measure the performance of modern light sources.

Luminous intensity and luminous intensity distribution

The luminous intensity of LED is a sign of its luminous intensity in a certain direction. Since the light intensity of LED varies greatly in different spatial angles, we have studied the light intensity distribution characteristics of LED. This parameter is of great practical significance and directly affects the minimum viewing angle of the LED display device. For example, for the large LED color display screen of the stadium, if the single LED tube is selected and distributed in a narrow range, the audience facing the screen at a large angle will see distorted images. In addition, traffic signs are also required to be recognizable by a wide range of people.

wavelength

For the spectral characteristics of LED, we mainly see whether its monochromaticity is good, and pay attention to whether the main colors of red, yellow, blue, green, white LED are pure. Because in many occasions, such as traffic signal lights, the color is strictly required. However, it is observed that some LED signal lights in China are blue in green and dark red in red. From this phenomenon, it is very necessary and meaningful for us to conduct special research on the spectral characteristics of LED.