How to detect the quality of led lighting?

14/01/2022

How to detect the quality of led lighting?

With more and more lamps and lanterns on the market, there are more and more basis for defining the quality of a lamp, but in the final analysis, the quality of lamps and lanterns mainly depends on the quality of the light presented. So today we can dig a little deeper, how do you determine the right quality of light to render true colors? The quality of the test led light has the following very important indicators as a reference:

Color Rendering Index (CRI):
The Color Rendering Index, commonly referred to as CRI, is a method we can use to measure how colors appear to the human eye, depending on the light source compared to the sun. The CRI provides a range of values ​​up to 100, where 100 is the best color rendering quality and values ​​below zero indicate very poor color rendering. The higher the CRI value (also known as CIE Ra), the more accurate the color. Basically, this CRI value helps us determine how well a light source can display color to the human eye.
How is CRI calculated?
Calculate the CRI value of the light source from the test color. The International Commission on Illumination (CIE) established a scale of 8 CIE standard color samples for the CRI method. In rare cases, 7 other colors can be used, but usually only 8 colors are used to measure the CRI value. The test involves comparing eight color samples under a light source, which is then compared to a reference light source (usually the sun). Then subtract 100 from the average difference to obtain the CRI value. This is why light sources that display more "true" colors have higher CRI values, and the average difference between the light source and the reference light is smaller.

IESTM-30-15:
The Illuminating Society of North America (IES) has released a new evaluation method (TM-30-15) for the color rendering ability of light sources. The deviation of average hue and chromaticity is displayed through color vector graphics, so as to have a more comprehensive understanding of light color quality, which can complement the insufficiency of traditional parameters (such as CRI) for evaluating the color of light sources. Currently, TM-30-15 is used with CRI, but it will eventually replace the CRI indicator. Because the difference between CRI's Fidelity Index and the TM-30-15 method is that the latter uses 99 color evaluation samples instead of just 8.

Color Quality Scale (CQS):
Another method we use to determine and analyze lighting quality is called CQS or Color Quality Scale. This is also due to the need to find alternatives to unsaturated CRI colors. Developed by NIST, there are 15 highly saturated colors for comparison of chromatic aberration, human preference and color rendering (the method evaluates 15 colors to more accurately span the range of normal object colors).
LED color temperature is to change the ratio of different lights. Increase the red light, the color temperature becomes warmer, and increase the blue light, the color temperature becomes colder. Change the size of the current flowing through the LED, the larger the current, the brighter, and vice versa. The regulation of the current is mostly realized by changing the PWM. The so-called PWM is pulse width adjustment. The most fundamental way to adjust the pulse width is to change the value of the resistor and capacitor values ​​that determine its width. The larger the product of RC, the larger the width.

Color temperature linear adjustment technology
The color temperature of the light source is obtained by comparing its color with the theoretical thermal black body radiator (referred to as a black body, an object whose absorption rate for radiant energy of any wavelength is equal to 1 at any temperature, is an ideal model, also called a complete radiator. ) to determine. The spectrum emitted by the thermal radiation light source is continuous and smooth. For a black body, the temperature is different, and the color is also different. There is a one-to-one correspondence between the color of a black body and its temperature. When expressing the color of a light source, the color of the light source is often compared with the color of the black body. If the color of the light emitted by the light source is the same as the color of the black body at a certain temperature, the color of the light source is regarded as a black body. The color at this temperature is called "color temperature".

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