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The common parameters such as luminous flux, illuminance and brightness were mentioned earlier. Let's talk about them in detail

Luminous flux Φ It refers to the intensity of light emission capacity, that is, the total amount of light emitted by the light source in unit time. It is generally indicated by the symbol Φ The unit of expression is expressed in lumens, and English is LM. It should be noted that the luminous flux is the luminous capacity of the light source, that is to say, the luminous flux of a product must have the luminous capacity. There is no luminous flux without luminous ability. In LED, it reflects the radiation power generated in the process of converting electric energy into light energy. Since we generally refer to visible light, it mainly refers to the luminous flux of visible light. The larger the luminous flux, the stronger the luminous capacity of the light source. Generally, the luminous flux value will be marked on the lamp for convenience of calculation. An instrument for measuring luminous flux is called an integrating sphere. The luminous flux indicated on the lamp is measured through this.

Illuminance e refers to the degree to which the surface of an object is illuminated, and is the luminous flux obtained per unit area. It is generally expressed by the letter E, with the unit of lux and LX in English. This is often used in our lighting. For example, the illuminance required by the general living room is about 150lx, while the illuminance required for reading is generally about 300lx to 500lx. However, the national level a illuminance and the national level AA illuminance that we often talk about are measured by the illuminance unit LX. For example, on a clear moon night, the illuminance is about 0.2lx, while the illuminance of sunlight is relatively high. The direct illumination illuminance is 100000lx, and the scattering illuminance also reaches 1000lx. Therefore, it is not recommended to read under the sunlight. The illuminance is too high, which is not good for the eyes.

Luminous intensity I, i.e. light intensity, focuses on the directionality of light, indicating the intensity of light emitted in a certain direction. It is generally expressed by symbol I, and the unit is candela, and expressed by CD.

We can also get the conversion relationship between the three

Φ= E*S

Φ= I*Sr

I= Er2

Luminous flux = illuminance X Area

Luminous flux = light intensity * solid angle

Light intensity = illuminance x square of radius

Luminous flux, light intensity and illuminance are closely related, indicating the performance of different characteristics of light in quantity. The above equation is mainly applicable to point light sources.

Another parameter is brightness, which also measures the luminosity of light. Brightness reflects the luminescent capacity of the surface of the light emitter or reflector. This parameter is closely related to people. We often say whether the space or object is bright or not. For example, whether the room is bright or not is the brightness that pays more attention to subjective feelings. A desk lamp may have a high luminous flux, but because the table top has a strong light absorption capacity, the brightness of the table top may not be bright enough. Brightness reflects the ratio of the light intensity in this direction to the luminous area seen by the human eye when observing an object. Therefore, this data is closely related to people. An object with brightness does not have to be a light emitter, that is, it does not have to be a light source, because reflection can also have brightness, which is significantly different from luminous flux.

As far as general lighting is concerned, these are the parameters and data that we mainly focus on. In addition, since light is actually an electromagnetic wave, there are also some other relevant data that we can temporarily ignore. For example, various infrared rays and ultraviolet rays are invisible to us. For example, visible light and invisible light are included in the sunlight. They may have some energy differences, but in the general lighting related knowledge, these are less involved. We can probably know about them.

Once you are familiar with these parameters, you can better understand light.