With the continuous growth and development of LED technology, a prominent need for standardized as well as consistent procedures for testing LED is observed. For more reliable results to test such technology, the testing standard LM-79 was set forth by the Illuminating Engineering Society of North America, also known as IESNA. Only complete LED lamps or LED luminaires are covered under the LM-79 standard. This article will be exploring LM-79 testing with respect to Goniophotometer and Integrating Sphere.
Contents
Workings of a Goniophotometer 2
Benefits of using Goniophotometer 2
Workings of an Integrating Sphere 3
Benefits of using Integrating Sphere 3
Table of Contents
Goniophotometer
A Goniophotometer is an instrument used to measure luminescence, color as well as the density of light. A moving detector goniophotometer, such as LISUN’s LSG-6000, is commonly used to test out all kinds of light sources glowing motion, like that of plant lighting, flood lights, street lamps and Light Emitting Diode, commonly known as LED amongst others. Its operation is dependent upon a photometer having a rotating arm that is fitted along with a roundabout mirror. As the arm of the instrument pivots, light hits it at various points, which then provides data regarding power circulation, iridescent transition and source productivity. This instrument complies with the requirements of the LM-79-19 standard and can measure light through an automatic light distribution intensity 3D curve testing system.
Workings of a Goniophotometer
A Goniophotometer works on a principle of fixed detector along with a rotating lamp method. On a two-dimensional rotating work table, a measuring lamp is installed. The rotating worktables rotating center corresponds to the luminous center of the lamp. This is done through the laser sight’s laser beam.
LM-79 only allows the use of type C goniophotometers to assure accuracy and consistency. The DUT is held in place as sensors revolve around it on several axes, measuring the intensity of the light it emits every few degrees of rotation. Since the DUT is held stationary and only the sensors move in type C goniophotometers, inaccuracies areminimized.
Benefits of using Goniophotometer
A goniophotometer is greatly beneficial in gauging the absolute brilliant motion of the lights and luminaires being tested, which are relatively bigger in size. It estimates the exact reliance of the products being tested and also aids in assessing their iridescent motion, spatial shading circulation as well as radiant force supply.
Integrating Sphere
An Integrating Sphere is utilized to figure out the light source’s exact location as well as the illumination that is divided into each point in space. It is essentially a hollow sphere with a high reflectivity which is used to assess luminosity, chromaticity coordinates, CCT, dominant wavelength, and peak wavelength for light sources and luminaries, among other things.
The integrating spheres are used in conjunction with a spectroradiometer to measure the light from single LEDs and LED lighting devices. The photometric, colorimetric, and electrical properties of LEDs should all be checked.
Workings of an Integrating Sphere
A light source is placed either in front of the opening of the sphere to take an irradiance measurement or within the integrating sphere to capture the whole radiant flux to take a measurement. Light rays will bounce many times on the reflecting coating in each of these measurement setups, resulting in a uniform light distribution throughout the integrating sphere. A small portion of the light is reflected and caught by the detector, similar to a spectroradiometer, via a baffle.
Benefits of using Integrating Sphere
The integrating sphere system is ideal for measuring the total luminous flux and color of integrated LED lights and small LED luminaires. This system has the advantage of being able to make quick estimations and does not require a dull environment. The temperature inside the circle isn’t affected by the variations that may exist in a temperature-controlled room because air development is limited.
Conclusion
Although the use of LED’s has rapidly increased in this day and age, the issue surrounding its quality and durability still persists. It is pertinent to utilize both goniophotometer and integrating spheres in testing of LED’s during production to figure out where exactly the issues lie so that they can subsequently be fixed.
