1, photometric determination
2, luminous flux and luminous efficiency detection
Luminous flux is the sum of the amount of light emitted by the light source, that is, the amount of luminescence. Test methods are mainly the following two. LED Panel Lights
(1) integrated method
(2) Spectral method
3.Spectral characteristics detection
The spectral characteristics of the test includes spectral power distribution, color coordinates, color temperature, color rendering index and other content.
Light intensity with the spatial angle (direction) of the changing relationship is called the pseudo-intensity distribution, the closed curve connected by this distribution is called the light intensity distribution curve. Because there are more measurement points, each point is subject to data processing, generally using automatic distribution photometer for measurement.
5, the effect of temperature on the optical properties of LEDs
Temperature has an impact on the optical properties of LEDs. Many experiments have shown that the temperature has an effect on the emission spectrum and color coordinates of LEDs.
6, ground brightness measurement
The luminance of a light source in a certain direction is the luminous intensity per unit projection area in that direction, generally using surface luminance meter, aiming luminance meter to measure the surface luminance, there are 2 parts of aiming light path and measuring light path.
7, LED lamp electrical parameters of the measurement
LED lamp electrical parameters mainly include positive, negative and negative three electrical parameters, which are related to the normal operation of the LED lamp and are one of the bases for judging the basic performance of the LED lamp. There are two ways to measure the electrical parameters of LED lights: one is a certain current, the second is to measure the voltage parameters; the second is to measure the current parameters when there is a certain voltage. The following measures are taken.
(1) forward voltage
Apply a positive current to the tested LED lamp, the LED lamp will produce a voltage drop across the ends. By adjusting the current value determined by the power supply, record the corresponding reading on the DC voltmeter, that is, the forward voltage of the LED lamp. According to the relevant common sense, the LED positive conduction when the resistance is small, using the ammeter external method more.
(2) reverse current
Apply reverse voltage to the test LED lamp, adjust the voltage regulator, the amperometer reading for the reverse current of the LED lamp under test. As the LED reverse conduction resistance is larger, so use the ammeter internal method to measure the forward voltage of the LED.
8, LED lamp thermal characteristics test
The thermal characteristics of the light-emitting diode has an important impact on the optical and electrical properties of the LED. Thermal resistance and junction temperature are the main thermal characteristics of LED2. Thermal resistance is the thermal resistance of the PN junction to the surface of the shell, that is, the ratio of the temperature difference on the heat flow channel to the power dissipated on the channel, and junction temperature is the junction temperature of the LED.
LED junction temperature and thermal resistance are generally measured by: infrared microimage method, spectroscopy, electrical parameters, photo-thermal resistance, etc. Using infrared temperature microscopy or micro thermocouple, the temperature of the LED chip surface temperature measurement, the accuracy is not enough.
The current widely used electrical parameter method is to use the positive voltage drop and PN junction temperature into a linear relationship, using the LEDPN junction forward voltage drop difference to obtain the LED junction temperature.