LED street lamp manufacturer summarizes the methods for testing LED lamps and lanterns:
1. Detection of luminescence intensity.
Light intensity or light intensity is the amount of light emitted at a particular Angle. CIE127 standard provides measurement conditions A (far field condition) of the light intensity measurement, measurement condition B (near-field conditions) of the two measuring the average LED light intensity of the measurement method of relatively concentrated in this case close, do not apply to the inverse square law of Yu Guangjiang conditions, two kinds of conditions for 1 cm2 area detector. Normally, the emission intensity is measured using standard condition B.
2. Detection of luminous flux and luminous efficiency.
The luminous flux is the sum of the amount of light emitted by the source, that is, the amount of light. There are two methods for detection:
(1) integral method. In the integral sphere, standard lights and measured lamps are lit in turn, and their readings at the photoelectric converter are recorded as Es and ED respectively. Standard Φ s luminous flux is known, the luminous flux is measured Φ D = ED x Φ s/Es. Integral method "point source" principle, simple operation, but by standard lamp and affected lamp color temperature error, measurement error.
(2) spectrophotometry. The luminous flux is calculated from the spectral energy P. Using a monochromator, the 380nm ~ 780nm spectra of standard lamps are measured in the integral sphere, and then the spectra of thematic lamps are measured under the same conditions, and the luminous flux of the measured lamps is calculated and compared.
The luminous efficiency is the proportion of the luminous flux emitted by the source and the power consumed by the light source, and the luminous efficiency of the LED is usually measured by the constant current method.
3. Spectral feature detection.
LED spectrum features, including spectral power distribution, color coordinates, color temperature, color rendering index, etc.
The spectral distribution indicates that the light source is composed of colored radiation of different wavelengths, and the radiation power of each wavelength is different, which is called spectral power distribution in different order with the wavelength of the light source. Use spectrophotometer (monochromator) and standard light to measure light source.
The chromaticity coordinates are the amount of luminous colors representing the light source on the graph in numerical terms. The color coordinate diagram can be used in various coordination systems, usually in X and Y coordinates.
Color temperature is the number of light source color table (color representation) seen by the human eye. The light emitted by the light source is the same as that of the absolute blackbody at a certain temperature, and the temperature is the color temperature. In the field of illumination, color temperature is an important parameter to describe the optical properties of light source. The color temperature theory comes from the black body correspondence, which can be obtained from the color coordinates of the light source containing the black track.
The color rendering index indicates that the light emitted by the light source is correctly reflected by the color of the object being illuminated. It is usually represented by the usual color index R a, which is the arithmetic mean of the color index of the light source. The color index is an important parameter for the quality of the light source, which determines the application of the light source, and improves the LED color rendering index is one of the important tasks of LED research.
4 light intensity distribution test.
The relation between the light intensity and the intensity distribution of the spatial Angle (direction) is called the false, and the closed curve is called the light intensity distribution curve. Because the measurement points are much, and each point is processed by data, automatic distribution photometer is usually used for measurement.
Effect of temperature effect on optical properties of LED.
Temperature affects the optical properties of leds. Can explain a lot of experiments, temperature affects LED emission spectrum and color coordinates.
Surface brightness measurement
The brightness of the light source in a certain direction for the light source in the direction of the projection direction unit of luminous intensity, the use of surface luminance meter, general collimator to measure the surface brightness, light path and metering 2 line of sight.