LED article to bring you to understand the top ten LED lighting quality indicators

Lighting quality refers to whether the lighting source meets the lighting indicators such as visual function, visual comfort, safety and visual beauty. Correct application of lighting quality indicators will bring new feelings to your lighting space, especially in the era of LED lighting, the quality of lighting is extremely important. The use of lighting quality indicators to purchase LED light source products will bring more effort with less effort. Effect, below, we introduce the main indicators of lighting quality.

1, color temperature

It is the light color of white light. The difference between white light color is red or blue. It is expressed by absolute temperature and the unit is K (Kelvin). Generally, the color temperature range of indoor lighting is 2800K-6500K.

Illuminating white light, the most typical is sunlight. It is well known that sunlight is a mixture of light of various colors. Among them, the most important ones are red, green and blue. (The picture on the right is an exploded view of the light passing through the prism, which verifies that the sunlight is a mixture of light of multiple colors.)

White light uses color temperature indicators to describe light color. When there are many blue light components in white light, white light color is blue (cold cold, such as northern winter noon sunshine). When there are many red light components in white light, white light color is partial. Red (warm, such as morning and evening sunlight), color temperature is the only way to express white light color.

The white light of the artificial light source is also formed by the mixing of light of various colors. For artificial light sources, we also describe the light color of white light with color temperature. For the physical analysis of white light, we usually use the method of spectral analysis. The spectral analysis of white light requires specialization. Instrument test production. The figure below is a variety of spectra.

It can be seen from this figure that the spectral composition of sunlight is rich and full. The spectral distribution of incandescent lamps and LED lamps in artificial light sources is better than that of high-pressure sodium lamps and fluorescent lamps. The spectrum of fluorescent lamps contains harmful ultraviolet components, due to incandescent lamps. It consumes a lot of energy and will be eliminated. The LED light source will be the leading product of the illumination source.

When describing white light color, many people use warm white light, natural white light, daylight white light, and cool white light classification. For the quality of illumination, this classification range is too large. Color temperature should be used to describe white light. Usually, LED white color temperature and white light The correspondence between light colors is as shown in the left figure below (slightly described). The international standard color temperature distinction should be based on the CIE1931 chromaticity diagram, as shown in the right image below:

Accurate color temperature values ​​are tested by professional instruments. When purchasing lighting products, describing color temperature is a problem that is bothering. In order to have an intuitive understanding, we have created a color temperature visual legend that visually distinguishes the color temperature of lighting products. As shown below:

2, color rendering

It is the degree of reduction of the color of the surface of the illuminated object by the illumination source. It is represented by the color rendering index Ra. The Ra range is from 0-100. The closer the Ra value is to 100, the higher the color rendering property, and the better the color reduction of the surface of the illuminated object. The color rendering of the light source requires professional instrument testing.

It can be seen from the spectrum of the sun that the solar spectrum is the most abundant, and it is the light source with the best color rendering. The color rendering of artificial light source is always lower than that of sunlight. Therefore, the best way to identify the color rendering of artificial light source is to The easiest way to compare sunlight is to compare the color of the palm or face with sunlight and artificial light. The closer to the color under the sun, the better the color rendering. You can also palm your hand to the light source and see the palm. The color, if the color of the palm of the hand is gray or yellow, the color rendering is not good. If the color of the palm of the hand has blood red, the color rendering is normal (as shown below):

For LED light sources, Ra can be roughly divided into three levels, Ra is less than 69, Ra is between 70 and 79, and Ra is greater than 80. For high-quality indoor lighting, a light source with Ra greater than 80 should be used. The color rendering index and the degree of color reduction can be referred to the visual comparison of the following figure.

China adopts the test standard of CIE. For LED light source, the general color rendering index Ra does not reasonably reflect the color rendering performance of LED illumination source. CIE also does not provide new test standards. For users who are pursuing high color rendering ability, Referring to the Planck curve in the CIE1931 chromaticity diagram (black line in the figure below), the closer the coordinate value of the test is to the light source of the Planck curve, the better the color rendering ability.

3. Illumination value of the light source

The illuminance is the luminous flux that the light source illuminates on the unit area of ​​the object to be illuminated. It is the degree of lightness and darkness of the surface of the illuminated object. It is represented by Lux Lux (Lx). The higher the illuminance value of the illuminated surface, the brighter the object is illuminated.

The illuminance value has a great relationship with the distance from the light source to the object to be illuminated. The farther the distance is, the lower the illuminance value is. The illuminance value is also related to the light distribution curve of the luminaire. The smaller the light output angle of the luminaire, the higher the illuminance value. The higher the light output angle, the lower the illuminance value; the illuminance value requires special instrument testing.

From the photometric point of view, luminous flux is the main indicator. As a lighting product, it mainly reflects the degree of light and darkness of the surface of the irradiated object. The illuminance value is used to describe the lighting effect more accurately. The illumination value of the indoor lighting is high and low, and the reaction is indoor lighting. Bright and dark, too high illumination and too low illumination have an impact on the health of the human eye. Therefore, the illumination value of indoor illumination needs to refer to the national standard (Table 1). The illumination value recommended according to this table does not appear. Excessive or too low illumination.

Table 1 Illumination standard values ​​of residential building lighting

4, the light distribution curve of the lamp

The indoor lighting effect is related to the layout of the luminaire and the light distribution curve of the luminaire. A good lighting effect is reflected in the reasonable lighting layout and the correct application of the light distribution of the lamps. The layout of the lamps and the light distribution of the lamps determine the visual function and visual comfort of the indoor lighting, reflecting the three-dimensional sense and layering of the lighting space. Among them, the light distribution application of the luminaire is appropriate, which can improve the lighting quality of the entire lighting space.

The purpose of the luminaire is to fix and protect the light source, as well as to decorate and beautify the environment. Another purpose of the luminaire is to redistribute the light output of the light source so that the light of the light source outputs light according to the light output angle of the luminaire design. This is called the light distribution of the luminaire. The light distribution curve of the luminaire is to describe the light output form of the luminaire. The smaller the light distribution angle, the brighter the sensation, and the light distribution curve of the luminaire is tested by special instruments. The figure below shows the light distribution curve commonly used in lamps.

The light distribution of the luminaire is related to the lighting function of the luminaire. The track spotlight and ceiling light generally adopt 15 or 30 light distribution, the downlight generally adopts 30 degree or 60 degree light distribution, and the bulb and ceiling lamp are generally 120 degree light distribution. . The light distribution of the lamp panel is between 60 degrees and 90 degrees.

5, the luminous efficiency of the light source

The brightness of the light source is described by the luminous flux. The luminous flux unit is lumens (lm). The larger the luminous flux, the higher the brightness of the light source. The ratio of the luminous flux of the light source to the power consumption of the light source is called the luminous efficiency of the light source. The unit is lm. /w (flow per lumen)

The luminous efficiency of the light source is an important indicator to measure the quality of the light source. The higher the luminous efficiency of the light source, the more energy-saving the light source, the luminous efficiency of the LED light source is about 90-130 lm/w, and the luminous efficiency of the energy-saving lamp is 48-80 lm/w. The luminous efficiency of incandescent lamps is 9-12 lm/w, and the luminous efficiency of poor quality LED light sources is only 60-80 lm/w. The products with high luminous efficiency and the quality of the light source are relatively good.

6, lighting efficiency

Indoor lighting seldom uses light source illumination alone. Usually, the light source is placed in the luminaire. After the light source is placed on the luminaire, the light output of the luminaire is lower than the light output of the single light source. The ratio of the two is called luminaire efficiency, and the luminaire efficiency is high. It shows that the manufacturing quality of the lamps is good, the energy-saving indicators of the lamps are high, and the lamp efficiency is an important indicator to measure the quality of the lamps. By comparing the efficiency of the lamps, the quality of the lamps can also be indirectly evaluated.

The relationship between the luminous efficiency of the light source, the efficiency of the luminaire, and the illuminance value of the luminaire is that the luminous flux output by the luminaire is only proportional to the efficiency of the luminaire, and the illuminance value of the luminaire is proportional to the luminous efficiency of the illuminating light, and the illuminance value of the luminaire is matched with the luminaire. Light curve is related, the illuminance value is high, it does not mean that the luminous flux is high, and the light source with high luminous efficiency of the light source is placed in the lamp with low efficiency of the lamp, the lumen output of the lamp will be greatly reduced, and the luminous efficiency of the light source and the efficiency of the lamp are higher, the illumination The higher the energy-saving index, the luminous efficiency of the light source and the efficiency of the luminaire are important indicators for measuring high-quality lighting products.

7, glare

It means that the light of the light source causes the visual discomfort of the human eye. Generally speaking, when the light source is glaring, the light source has glare.

On the streets of the night, when the car with the high beam lights comes on the way, the glare we see is the glare. As shown on the right, the indoor lighting also has glare problems. The glare can make people feel uncomfortable and even cause For the short-term blindness, the glare of indoor lighting has the greatest impact on children and the elderly, and glare affects the quality of lighting, which is a problem worthy of attention.

The glare problem and the indoor illuminance and lighting energy-saving indicators are mutually constrained. If a single light source is bright enough, there will be glare problems, that is, the so-called "sufficient light will be dazzling", glare problems, weigh the pros and cons, comprehensive consideration; the greater the luminous flux, the glare The higher the illuminance value, the higher the glare; the smaller the light distribution angle of the lamp, the higher the glare; the lower the brightness, the lower the glare, but the energy saving index will also decrease; the control of the glare problem is based on visual comfort. The principle is controlled; for those with old people and children, more attention should be paid to the control of glare.

8, stroboscopic

The stroboscopic light source is a phenomenon in which the brightness of the light source changes with time and brightness. When working under a stroboscopic light source for a long time, it will cause visual fatigue. The stroboscopic time of the largest light source is 0.02 seconds, and the visual retention time of the human eye. It is 0.04 seconds.

The strobe time of the light source is faster than the visual retention time of the human eye, so the human vision almost does not feel the light source flashing, but the visual cells of the human eye will sense it, which is the cause of visual fatigue, and the light source flashes. The higher the frequency, the lower the visual fatigue caused by stroboscopic light. We call it the low-frequency flash, which will affect the health of the human eye and affect the quality of lighting.

The strobe of the light source is not visible to the human eye, so how to check it? Here is a simple and effective way to identify the strobe of the light source, use the camera's camera function to align the light source, and adjust the appropriate distance. When there are bright and dark stripes on the screen, the light source has strobe, if the stripe interval is obvious, The strobe of the light source is large, and there are obvious light and dark stripes on both sides of the light source, indicating that the strobe is large. If the light and dark stripes on the screen are few or very thin, the strobe is low; if the light and dark stripes are hardly visible, the strobe is very low, but Not all mobile phones can see strobe, some mobile phones can't see strobe, when testing, it is best to try a few more mobile phones.

9, the safety of lighting equipment

The safety of lighting equipment includes electric shock problems, electric leakage problems, high temperature burn problems, explosion problems, installation reliability, safety signs, and application environment signs.

The safety of lighting equipment is restricted by the relevant national standards. In general, we can observe the appearance quality of the product, the certification mark, the process quality of the driving power supply, and the related data provided by the product. The simplest method is the price of the lighting product. Products with high prices, high relative reliability, and products with too low prices should be alert, that is, the so-called cheap and not good goods.

Then, how to judge the price of lighting products, recommend a simple method of judging, is to calculate the price per watt, if the price per watt is lower than the average value, this product needs to be cautious; determine the price per watt of the light source The premise is that the actual active power of the light source is actually measured. There are many LED light sources with the same nominal power as the energy-saving lamps, which are all virtual high.

10. Energy-saving indicators of lighting equipment

The highest level of lighting is visual beauty. In order to enjoy this beauty, it will be turned on for a long time to enjoy. If the lighting source consumes too much power, it will cause the user to have a psychological burden due to the electricity bill, causing a decline in visual beauty, which indirectly reduces Lighting quality, therefore, we also included lighting energy efficiency indicators into lighting quality indicators.

Related to lighting energy efficiency indicators are:

1) The luminous efficiency of the light source.

2), lighting efficiency.

3), the effect design of the lighting space and the reasonableness of the illumination space illumination value.

4), the power efficiency of the drive power supply.

5), the heat dissipation performance of the LED light source.

We focus on the efficiency of the light source driving power supply and the heat dissipation problem of the LED light source. For the LED light source, the higher the efficiency of the driving power source, the higher the luminous efficiency of the light source, and the more energy efficient the light source; the power efficiency and the power factor of the power source are two different. The concept of both is high, indicating that the quality of the drive power is good.

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