First, the principle and purpose
The degree to which a light source appears to the color of an object is called color rendering, which is the degree of color fidelity. The light source with high color rendering has better color reproduction, and the color we see is closer to the natural primary color; the light source with low color rendering has poorer color reproduction, and the color deviation we see is also large. The color rendering index (Ra) is currently a common method for defining the color rendering of light sources. For artificial light sources, color rendering is a very important chromaticity parameter, which indicates the deviation of the color of the object when it is illuminated by the light source than when the reference light (sunlight) is illuminated. CIE recommends a method for quantitatively measuring the color rendering of a light source. The color rendering index Ra is distributed within 0 to 100. When Ra=100, the color rendering property is the best, and the smaller the value, the worse the color rendering property.
The International Commission on Illumination CIE has developed a way to quantify its color rendering based on eight standard color samples, that is, first measure the color temperature of the measured light source, and then calculate the reference light source with the same color temperature under this light source. The deviation rate of the eight color samples, and the data comparing the ratios of the eight color samples is called the color rendering index. The difference in the data of this test method is very large. Currently, we are using specialized instruments to measure color parameter values â€‹â€‹including chromaticity coordinates, correlated color temperature, and color rendering index. The instrument that often uses light and color measurement in the test is the PMS-50 (Enhanced) UV-Vis-NIR spectroscopy system, which is based on the International Commission on Illumination CIE standards for light and color measurement. The electromagnetic wave emitted by the LED lighting fixture in the special wavelength range of 380 nm to 780 nm is precisely because the human eye responds to "bright" and "color" in this band, so the measurement and measurement for this band are equivalent. important.
According to the "Design Specification for TV Studio Lighting System", color TV lighting requires that the color rendering index of the light source be no less than 85. If the color rendering index of the light source is too low, the color reproduction of the TV screen will be greatly affected. That is to say, a light source with a color rendering index below 85 cannot be used in a television studio. As an emerging light source, LED lighting fixtures meet the requirements of color TV lighting and need to test their display index in the laboratory. At the same time, the color rendering index of LED lamps of various manufacturers is different, and there is a gap between the color rendering index of traditional tungsten halogen lamps. Therefore, LED lighting fixtures will have certain influence on the color reproduction of TV images when used in the studio. By comparing LED lighting fixtures in the studio with traditional tungsten halogen lamps, to understand the degree of influence of LED lighting fixtures on the color reproduction of TV images and the factors that may affect the color reproduction of TV images, LED lighting fixtures can restore the color of TV images. The impact test is rated as the main observation.
Second, laboratory testing
1. Test conditions
1.1 Measuring instruments
PMS-50 (enhanced) ultraviolet-visible-near-infrared spectroscopy system produced by Hangzhou Yuanfang Optoelectronic Information Co., Ltd.
1.2 Variety and quantity of lamps
The color rendering of this LED lighting fixture will be tested on halogen tungsten spotlights, LED flat light lamps and LED spotlights. These three types of lamps choose seven types of lighting fixtures, two of which are tested for each type of lamp. Among them, we also test the color rendering after the high temperature test for the 3-1 LED50W flat soft light. Product model and luminaire number are shown in Table 1.
The color rendering of LED general lighting fixtures is arranged in the laboratory. During the test, 2 LED lamps are provided for each model. The LED lamps can be properly adjusted before testing, and the lamps are ignited for 100 hours. The test is not allowed. Exchange LED luminaires, one for each type of LED.
2. Test content, methods and steps
2.1 Test content
According to the photometric colorimetric theory, as long as the spectral power distribution P(Î») of the measured light source is measured, the color parameters of the measured light source can be calculated: chromaticity coordinates (x, y) and (u, v), correlation Color temperature Tc, color rendering index Ra, Ri (1 to 15), peak wavelength, half width, and the like. Therefore, the specific experimental method is to measure the spectral power distribution P(Î») of the LED lighting fixture using the PMS-50 (enhanced) ultraviolet-visible-near-infrared spectroscopy system of light and color measuring instruments.
PMS-50 (enhanced) UV-visible-near-infrared spectroscopy system was tested with PMS-50 (enhanced) UV-Vis-NIR spectroscopy system. Fully meet the CIE requirements for light and color measurement. The measurement system includes a PMS-50 host, a photometric probe, a temperature probe, a small integrating sphere, a regulated power supply, a smart fuel gauge, a dedicated serial communication cable, and special software.
2.2 Test equipment
PMS-50 (enhanced) UV-visible-near-infrared spectroscopy system was tested with PMS-50 (enhanced) UV-Vis-NIR spectroscopy system for chromaticity coordinates, correlated color temperature, and color rendering index. 1) In principle, it fully meets the requirements of CIE for light and color measurement. The measurement system includes a PMS-50 host, a photometric probe, a temperature probe, a small integrating sphere, a regulated power supply, a smart electricity measuring instrument, and a dedicated serial communication cable. And special software.
Align the light exit of the lamp to be tested with the receiving window of the small integrating sphere. Pay attention to the position and direction of the light. Because the light source is different under different conditions, the test result is different. During the test, the light source must be illuminated for a while. (Generally 15-30 minutes) After the lamp is stable, test it again and save the test report after the test is completed.
2.3 Test methods and steps
The test is carried out in an environment where the surrounding walls, roof, floor and test equipment are matt black. First, the lamps to be tested must be lighted for a period of time (usually 15 to 30 minutes), and then tested after the lamp is stable. Secondly, align the light exit of the lamp to be tested with the receiving window of the small integrating sphere. Pay attention to the position and direction of the lighting. Because the light source is different under different conditions, the test result is different. Finally, save the test report after the test is completed. . For the spectral test of the spotlight, we tested the concentrating end and the astigmatizing end separately.
3. Test results and conclusions
3.1 Test results
The TMS-50 (enhanced) ultraviolet-visible-near-infrared spectroscopy system was used to test the halogen tungsten spotlights and LED lamps. Figures 2 and 3 show the two spectrograms after the test.
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