There are mainly chromaticity coordinates, dominant wavelength, color purity, color temperature and color rendering, etc. The test methods include spectrophotometry and integration method.
Spectrophotometry: Obtain the spectral power distribution of the LED lamp bead through the spectroscopic measurement of the monochromator, and then use the chromaticity expansion function to obtain the corresponding chromaticity parameter.
Integral method: Use specific color filter and photoelectric detector to directly measure chromaticity parameters.
2. The optical characteristics
Mainly includes luminous flux and luminous efficiency, light intensity and light intensity distribution characteristics and spectral parameters.
Luminous flux and luminous efficiency: There are usually two methods, the integrating sphere method and the variable angle photometer method. Although the other test results are the most accurate, they are generally used because of the time-consuming substitution. When testing with the integrating sphere method, the LED lamp bead to be tested can be placed on the center of the sphere or on the wall of the sphere. After the luminous flux is measured, the luminous efficiency of the LED lamp bead can be measured with the electrical parameter tester, that is, the light efficiency.
Light intensity and light intensity distribution characteristics: LED light beads have alternating light intensity distribution, so its test results vary with the distance of the test and the size of the detector position, allowing each LED light bead to perform light intensity under the same conditions Test and evaluation, so that the results are more accurate.
The spectral characteristics of LED lamp beads are all expressed by the spectral power distribution. Through the spectral power distribution, the chromaticity parameter can also be obtained. The test of the general spectral power distribution needs to be carried out by splitting, and the monochromatic light in the mixed light is distinguished one by one for measurement. A prism and a grating can be used for splitting.
The electrical characteristics of LED lamp beads include forward current, forward voltage, reverse current, and reverse voltage. These tests are generally performed by using a voltage and current meter, under the condition of constant current and constant voltage power supply. Through the test of the z electrical characteristics of the LED, the maximum allowable forward voltage, forward current and reverse voltage, current and other parameters can be converted, and the best working electric power value of the LED can also be obtained.
4. Switching characteristics
Refers to the light, electricity and color change characteristics of the LED lamp beads when they are powered on and off. Through this test, you can get the working rules of the LED lamp beads at the moment of power on and off, the changes in material properties, etc. Of loss.
Also refers to thermal resistance and junction temperature. Thermal resistance refers to the ratio of the temperature difference along the heat flow channel to the power dissipated on the channel. Junction temperature refers to the PN junction temperature of the LED lamp beads. There are two test methods for the LED lamp bead junction temperature. One is to measure the surface temperature of the LED chip using an infrared temperature microscope or a miniature thermocouple. The other is to use an inverse ratio between the positive tilt at a determined current and the junction temperature. Change the relationship to determine the junction temperature of the LED lamp beads.