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Analysis of 10 common LED terms

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1. What is the luminous intensity (luminosity) of the LED?

Answer: Luminous intensity (luminosity, I) is defined as follows: The luminosity of a point light source in a particular direction, that is, the amount of light emitted by an emitter in a unit time, also called luminosity, and the common unit of luminosity is candlelight (cd, candela). International candlelight is Defined as the luminosity of a candle made of fat, which burns 120 grains per hour, one grain of cold air is equivalent to 0.0648 grams.

 

2. What is the unit of luminous intensity (luminance)?

 Answer: The common unit of light intensity is candlelight (cd, candela). International standard candlelight (LCD) is defined as 600,000 points perpendicular to the black body (with a surface area of 1m2) when an ideal black body is at the freezing point of platinum (1769 ° C). One of the luminosities, the so-called ideal black body means that the emissivity of the object is equal to 1, the energy absorbed by the object can be radiated, so that the temperature has remained uniform and fixed, the international standard candle (candela) and the old standard candle (candle) are exchanged. The relationship is 1 candle = 0.981 candle.

 

3. What is luminous flux? What is the unit of luminous flux?

 Answer: The means of luminous flux (φ) is: the energy emitted by a dot light or a linear light in a unit of time, between which the visual person (the radiant flux that humans can feel) is called luminous flux. The unit of luminous flux is lumens (lm for short). One lumen (lm) is defined as the luminous flux that passes through an international standard candlelight source in units of solid arc angles. Since the perfect spherical region is 4πR2, the first-class luminous flux is equivalent to one candle. The luminous flux emitted is 1 / 4π, or the sphere is 4π, so by definition of lumens, we know that a cd point light source emits 4π lumens. In other words, φ (lumen) = 4πI (candle). Light), assuming that ΔΩ is a small three-dimensional arc angle, the luminous flux Δφ is a solid angle ΔΩ, and Δφ = ΔΩI.

 

4. What is the meaning of a standing candle?

 Answer: The light from a one-foot candle refers to the illuminance on the surface orthogonal to the light one foot away from the light source (point light source or non-point light source) of a candle. The luminous flux received at 1 square foot is the illuminance at 1 lumen and 1 foot c = 10.76 lux.

 

5. What is the meaning of a one-meter candle?

 Answer: The light from a one-meter candle refers to the illuminance on the surface orthogonal to the light at a distance of one meter from the light source (point light source or non-point light source) of candlelight, which is called lux (lux, also written as lx), which is per square meter. The luminous flux received inside is the illuminance at 1 lumen (lumens / m2).

 

6. What is the meaning of 6.1lux?

 Answer: Illuminance, when the luminous flux received per square meter, is 1 lumen

 

7. What is the meaning of illuminance?

 Answer: Illuminance (E) is defined as the luminous flux per unit area of the illuminated object, or the luminosity per unit area of the illuminated object per unit of time. The unit is in meter-candles or foot-candles (FTC) he said.

 

8. How is the relationship between illuminance, distance, luminosity?

 Answer: E (illuminance) = I (luminance) / r2 (distance squared).

 

9. What is the meaning of the light effect (lumens/watt, lm/w)?

 Answer: The ratio of the total luminous flux emitted by the light source to the electrical power (watts) consumed by the light source is called the luminous efficiency of the light source.

 

10. What is color temperature?

 Answer: When the color emitted by the light source is the same as the color radiated by the black body at a certain temperature, the black body temperature is the color temperature.