1. Luminous intensity detection Light intensity is the intensity of light, which refers to the amount of light emitted within a certain angle. Due to the concentration of light-emitting diodes, the inverse square law does not apply to short distances. The CIE 127 standard provides two conditions for measuring the average normal light intensity: measurement condition A (far-field condition) and measurement condition B (near-field condition). The detector area is 1 cm2 in both cases. Typically, the luminescence intensity is measured using standard condition B

2. Detection of luminous flux and efficiency The luminous flux is the sum of the amount of light emitted by the light source, that is, the amount of light emitted. Detection methods mainly include the following two: (1) integral method. The standard lamp and the measured lamp are ignited in the integrating sphere in sequence, and their readings in the photoelectric converter are recorded as Es and ed, respectively. If the standard luminous flux is called φs, the luminous flux of the measured lamp is φd = ed×φs/es. The integration method adopts the principle of "point light source" and is simple to operate, but due to the color temperature deviation between the standard lamp and the measured lamp, the measurement error is large. (2) spectrophotometry. The luminous flux is calculated from the spectral energy P(λ) distribution. Using a monochromator, the 380 nm ~ 780 nm spectrum of the standard lamp is measured on the integrating sphere, and then the spectrum of the measured lamp is measured under the same conditions, and the luminous flux of the measured lamp is calculated by comparison. Luminous efficiency is the ratio of the luminous flux emitted by the light source to the power consumed. The constant current method is usually used to measure the luminous efficiency of a light emitting diode.

3. Detection of spectral characteristics The detection of spectral characteristics of light-emitting diodes includes spectral power distribution, color coordinates, color temperature, color rendering index, etc. The spectral power distribution means that the light of the light source is composed of many different wavelengths of colored radiation, and the radiation power of each wavelength is also different. When the light sources are arranged in wavelength order, this difference is called the spectral power distribution of the light source. The light sources were compared and measured with a spectrophotometer (monochromator) and a standard lamp. The color coordinate is the amount of light emission color of the light source expressed numerically on the coordinate chart. The coordinate chart representing the color has a variety of coordinate systems, usually using the X and Y coordinate systems. Color temperature is the number of light color table (appearance color representation) that the human eye sees. When the light emitted by the light source is the same color as the light emitted by the black body at a certain temperature, the temperature is the color temperature. In the field of lighting, color temperature is an important parameter to describe the optical characteristics of light sources. The related theory of color temperature is derived from blackbody radiation, and can be obtained from the color coordinates including the blackbody locus through the color coordinates of the light source. The color rendering index represents the amount of light emitted by the light source that correctly reflects the color of the illuminated object. It is usually expressed by the universal color rendering index Ra, which is the arithmetic average of the light source color rendering index of the eight color samples. The color rendering index is an important parameter of the quality of the light source, which determines the application range of the light source. Improving the color rendering index of white light-emitting diodes is one of the important tasks of LED research and development.

4. The effect of temperature on the optical performance of light-emitting diodes Temperature will affect the optical characteristics of light-emitting diodes. A large number of experiments show that temperature will affect the emission spectrum and color coordinates of light-emitting diodes.

5. Measurement of electrical parameters of LED lamps. Electrical parameters mainly include forward voltage, reverse voltage and reverse current. They are related to the normal operation of LED lamps and are one of the basis for judging the basic performance of LED lamps. There are two types of electrical parameter measurement of LED lamps: voltage parameters under a certain current; when the voltage is constant, test the current parameters. Specific methods are as follows: (1) DC voltage. When a forward current is applied to the LED lamp to be detected, a voltage drop occurs across the LED lamp. Adjust the power supply determined by the current value, and record the relevant reading on the DC voltmeter, which is the DC voltage of the LED lamp. According to relevant common sense, when the light-emitting diode is on, the resistance is smaller and the external connection method of the ammeter is more accurate. (2) Reverse current. Apply a reverse voltage to the tested LED lamp and adjust the regulated power supply. The reading of the ammeter is the reverse current of the measured LED lamp. Similar to DC voltage measurement, due to the large resistance of the light-emitting diode during reverse conduction, the internal connection of the ammeter is used.