With the definition of the light curve of the test:
It refers to the intensity distribution of light (or lights) in all directions in space.
The light distribution curve test method (usually there are three methods):
1) The polar coordinate method
2) is the Cartesian coordinate method
3) light intensity curve

Polar coordinates with the light curve: the metering plane through the center of the light source, the measured intensity values of the lamps at different angles. Starting from a certain direction, the angle of the function, the intensity of each angle marked with vector, connecting the vector connection at the top of the lighting in polar coordinates with the light curve. If the lamp is the axis of rotational symmetry, is only the surface through the axis of a metering light intensity distribution curve can explain the intensity distribution in space, if the lamps light distribution in space is asymmetric, you need to a number of metering plane of the light intensity distribution curve in order to explain the intensity spatial distribution status.

Cartesian coordinate light distribution curve: concentrating lamps, because the beam is concentrated in a very small solid angle, it is difficult to use polar coordinates to express the spatial distribution of light intensity on the use of the notation at right angles from the light distribution curve to the vertical axis represents the intensity map I, horizontal beam angle of the cast, if it is with the symmetry axis of rotation of the lamp is only a light distribution curve to represent, if it is asymmetric lighting is required light distribution curve .

C, light intensity curves: the top of the intensity equal to the vector linking the curve known as the light intensity curve, arranged by a certain percentage will be adjacent to wait until the value of the light intensity curve, draw a series of isocandela curve consisting of The figure is called the circular network diagram, the rectangular network map and positive arc Map to wait until the light intensity map, Figure. Rectangular network diagram not only explain the intensity distribution of lamps, but also the regional distribution of the amount of light, Floodlights with light intensity curves are rectangular Map.

Light distribution curve instrument (Goniophotometer) Type CGoniophotometry space for lamps used to light intensity distribution of luminous flux, lamp efficiency, the illuminance distribution to assess the photometric characteristics of the data. Light distribution curve (brightness distribution) is an important factor affecting the lighting quality, so the tests are stringent requirements for site distance, temperature, light, with light curves (brightness distribution) laboratory in accordance with the International Commission on Illumination ( CIE) standard to establish fully meet GB/T.7002-2008, GB / T 9468-2008, GB/T24824-2009, GB/T24907-2010, CIE 69, CIE 70, CIE84, IESNALM-75/79, EN13032 -1, the U.S. Energy Star (semiconductor lighting), the European light source energy efficiency regulations and other standards set out in testing requirements.

       Light distribution curve refers to the intensity distribution of light (or lights) in all directions in space. The results of the test is to determine the lighting energy efficiency and use of data, general foreign professional sellers during lamps procurement, the light distribution curve generally provided as a basic parameter. The integrating sphere is: photometric hollow sphere. Balls coated with or without wavelength selectivity of the (uniform) diffuse reflectance of white paint. The ball in either direction of illumination is the same. At present, most large and medium-sized lighting manufacturers are self-configuring integrating sphere device, but mainly for the data reference and a brief report of the product design. For recognized with the light curve of the report, still need a professional third-party testing organizations, professional equipment and computing software to form a formal report format.

       Lumens of luminous flux unit. Luminous intensity of one candela (cd) a point source, the luminous flux emitted in unit solid angle (1 steradian) as "a lumen", the abbreviation (lm). In simple terms, this means showing the brightness of a candle candlelight in one meter (1 meter = 1 meter) away. An ordinary 40-watt incandescent bulbs, the luminous efficiency is about 10 lumens per watt and 400 lumens of light, it can be issued.
Approximate common light source luminous efficiency (lm / W) as follows:
Incandescent, 10 -20
White the LED 80-200
Fluorescent light, 50
Light of the sun, 94
Sodium lamp, 120
Energy-saving lamp 60 -80
LED ,80-130

LM-79 test report issued recently more and more American buyers require LED lamps, this one also slowly more and more the concern of various LED manufacturers. Integrating sphere of the general manufacturers can not meet the testing requirements of the standard, part of the project needs to make use of distributed photometer to complete, and a complete LM-79 test report these tests have requested.

IES LM-79-08 Description of the standard:
      IES LM-79-08 "solid-state lighting products, electrical and photometric measurement provides the total luminous flux measurement of solid state lighting (SSL), electrical power, luminous flux intensity distribution and chromaticity, shall comply with the procedures and precautions. The standard applies to LED-based, integrated control circuit and heatsink only need AC or DC power supply can run the SSL products; does not apply to require external operation circuit or an external heatsink (such as LED chips, LED packaging, LED modules SSL products, etc.). The standard 2 to Chapter 8 describes the various requirements of the products in the measurement. Measurement, ambient temperature and air flow measurements. Measuring the ambient temperature should be maintained at 25 ℃ ± 1 ℃, the temperature sensor and SSL products at the same height, the distance is not more than 1 meters, and avoid the direct exposure of SSL products and other light sources. SSL support device should be used to the poor thermal conductivity of the material (eg PTFE). The air flow measuring device should be small enough so as not to affect the normal air convection devices. Measurement also should be noted that the aging and stability of SSL products. Classification of new SSL products, you should direct measurements, without aging. Although some LED light source brightness in the beginning 1000 hours has increased, but due to the general increase of only a few percentage points, so little effect on the measurement results. Before the measurement, it should be above ambient temperature and air flow requirements to run for a certain time to reach steady state, the settling time is generally 30 minutes (small integrated LED light) to more than two hours (large SSL lighting equipment). When changes in the product within 30 minutes, three times the light output and electrical power readings (15 minutes reading time) does not exceed 0.5%, they think the product has reached a steady state. In addition, measuring the orientation of SSL products should be based on normal use of the state of the manufacturer's recommendations or product to be placed. Powered AC or DC power supply should be used when the normal operation of the product value, the voltage fluctuations shall not exceed 0.2%. The IES the LM-79-08 standard, the 9th chapter describes the test method of the total flux is measured using an integrating sphere system or goniophotometer. Integrating sphere system which applies to the total luminous flux and chromaticity measurement of the integrated LED lights and the small size of LED lighting, and its advantage is speed, no darkroom, air flow is small, and small temperature fluctuations. But the heat generated by the SSL products will accumulate leading to the ambient temperature of product testing. Integrating sphere system consists of two kinds, one kind of using V () associated with an optical head, another Spectroradiometer as a probe. The goniophotometer should be used for the larger size of the SSL products to measure, of course, goniophotometer can also be used to test the small size of SSL products. The goniophotometer generally used to measure the intensity distribution of lumens, and then calculate the total flux. The goniophotometer must be installed in the constant temperature darkroom, its advantage is that the test light source of heat does not accumulate. However, the the goniophotometer measurement time is longer, prone to spectral detuning. The standard Chapter 10 is the measurement of the lumens intensity distribution. The goniophotometer measuring the distribution of the lumens intensity, the distance of the photometer with SSL products should be more than 5 times the maximum size, the distance of the narrow-beam light source should be longer. SSL products, you should record its absolute circulation intensity distribution value (corresponding to the traditional lighting of the absolute photometry), and not with the traditional lighting relative photometry. For the electronic version of the lumens intensity distribution measured data, as necessary, according to the IES LM-63 IES file format to prepare. Chapter 11 of the IES LM-79-08 standard formula on lumen efficiency ηv,. ηv = ΦTEST / PTEST, units of lm / W The which ΦTEST the total luminous flux is measured by the and the PTEST the measured input power. Note lumen efficiency ηv, can not be confused with the efficiency of the radiation lumens, which is equal to the luminous flux divided by the radiation flux. Standard Chapter 12 is the color characteristics of SSL product testing methods, including the chromaticity coordinates, correlated color temperature and color index. Measurements can be used in two ways: Spectroradiometer integrating sphere system as a probe, three-dimensional scanning using a Spectroradiometer or colorimeter. Spectroradiometer wavelength range at least to cover 380 nm to 780 nm. Description of the measurement uncertainty, the standard 13 requirements, with 95% confidence level, and therefore contains the factor k should be 2. Described in Chapter 14 of the IES LM-79-08 standard SSL products to be tested in accordance with this standard, the product test report should contain, including: the test date and test agencies; manufacturer's name and the name of the SSL product testing; test the number of parameters (total luminous flux, luminous efficiency, etc.); related power value (an indication of the direct current (frequency) or AC), the test correlated color temperature of the name of the SSL products; before the test run time (a new product should be 0); including total running time, including the stabilization time; ambient temperature; orientation of SSL products in the measurement (light position); settling time; photometric method or instrument used (Spectroradiometer Spectroradiometer integral as probe ball system, goniophotometer); referenced by the standard name and type (power, light type intensity distribution types - multi / one-way), and source; the spectral detuning of the correction factor (eg, self-detuning intensity distribution, etc.); photometric conditions (the Spectroradiometer ball diameter, coating reflection coefficient, 4π or 2π structure; goniophotometer is the luminosity distance); measuring the total luminous flux (lm) and each SSL input voltage (V), current (A) and power (W); lumens intensity distribution (if applicable); color characteristics (chromaticity coordinates, correlated color temperature of white light products and / or color rendering index); spectral power distribution (if applicable); Spectroradiometer bandwidth (if the report dealing with the spectral distribution and / or color characteristics); use of equipment; uncertainty (if required); deviation and standard operating procedures (if any).