Flux (luminous flux, Φ)
Unit: lm (lumen, lm)
    Emitted by a light source and is aware of all of the human eye is called radiant energy flux .
Light intensity (luminous intensity, l)
Unit: cd (candela, cd)
    Sources within the three-dimensional flux angle size in a certain direction .
Generally , the light source will be different in different directions to emit the light flux intensity . The intensity of visible radiation emitted light intensity in a particular direction is called .
Illuminance (llluminance, E)
Unit: lux (Lux, lx)
    Illumination is the ratio of the flux of being face to face . 1lux of illumination 1lumen of flux uniformly distributed in an area of one square meter of the area.
Brightness (Luminance, L)
Unit: candela per square meter (cd / m )
    Brightness of a light source or one of its units to be face to face represents a surface in one direction of the light intensity density , it can be said that the human eye or face to face the bright light of the extent of this perception .
Color (Co1or Temperature)
Unit: absolute temperature (kelvin, k)
    The color temperature of a light source is defined as a standard black body with its light color of the same .
Of its absolute temperature, this temperature can be found in the corresponding point on the Planckian locus on the chromaticity diagram . The higher the standard blackbody temperature , the radiation out of the blue light spectrum , the more ingredients, the red component also less relative. To emit a warm white light color is an example of an ordinary incandescent light bulbs , color temperature of 2700K, the color and the color temperature of daylight fluorescent lamp is 6000K.
Light and radiation (Light and radiation)
    Just refer to the human eye can perceive as bright as electromagnetic radiation, it can be said that the entire spectrum of electromagnetic radiation in the visible portion of the human eye ; wavelength distribution in this part of the 360 to 830nm, only known to the electromagnetic radiation spectrum of the very small the part .
Luminous efficiency (Luminous efficacy)
Unit: lumens per watt [lm / W]
    On behalf of the light source will be converted into electrical energy consumed in the efficiency of light
Not visible (lnvisible light)
    With respect to visible light, the wavelength of the electromagnetic radiation outside the 360 to 830nm is called invisible light. Electromagnetic wavelength less than 360nm most ordinary people understand the ultraviolet , there are other X -ray , r -rays, cosmic rays ; larger than the electromagnetic radiation of 780nm infrared and radio waves .
Spectrum (Spectrum)
    By order of the wavelength of the light distribution of the called spectroscopy. Each source can be composed according to their wavelengths and shows its spectral energy distribution (Power Spectrunm Distribu-tion) in the spectra . Spectrum sunlight and incandescent bulbs are energy distribution is a continuous curve , and the general non- discharge lamp is a continuous curve .
A light emitting diode (LED)
    Pn diode emitting diodes made of special material . Under bias , electrons in the joints mobile , it will glow in the process of binding to destroy in Hue . Small size, high luminous efficiency is not the original , but in recent years the rapid development of the occasion has been extended to apply to the traffic lights, lights , or even for lighting purposes some special occasions .
CRI (Color rendering)
    Artificial light is generally considered to be correctly perceived by the human eye color , just like to see the same thing in the sunlight . Of course, this depends on the occasion and purpose of applications have different degree requirements. This quasi- It that is the color rendering properties of light source , known as the "average color rendering index (general color rendering index, (Ra)." Average color rendering index of the object displayed under a light source of color and its reference to under the light source the relative difference between the colors. their assessed value of the law were to reference color rendering of the light source and the light , the better the test , the average color rendering index Ra 100 of the light source can make a variety of colors presented as the reference light being illuminated color the lower the Ra value , the more distorted the colors presented .
Incandescent bulbs (lncandescent lanp)
    Incandescent bulb is the first mature artificial electric light, it is the use of the principle of the filament heating power glowing light. Generally , the lower the efficiency of incandescent light emission life is short , but convenient to use .
Gas discharge lamp (Gas discharge lamp)
    Such a light source for emitting principle of interstitial gas between two electrodes by electron excitation light. Can be divided into low-pressure gas discharge lamps such as fluorescent lamps and high-pressure gas discharge lamps , such as mercury vapor lamps , high pressure sodium vapor lamps and metal halide lamps .
Lighting efficiency (Luminaire efficiency)
    Lamp efficiency ( also known lamp light output ratio ) is an important criterion to evaluate the energy efficiency of the lamps , the light flux whose value is given by dividing the lamp with a light source device of the quotient resulting flux emitted by the light source itself .
Metering important formula:
    I, the light intensity [cd] = flux within the solid angle , solid angle Ω [sr]
    E, illuminance [lx] = fall on an area of the luminous flux [lm] / This is face to face area [ m ] = light intensity [cd] / ( distance [lm])
    L, luminance [cd / m ] = light intensity [cd] / 's been seen face to face area [ m ]
   η, luminous flux efficiency [lm / W] = generated [lm] / electric power consumption [W]