How exactly do the integrating spheres function

The use of LEDs has increased with the advancement of technology. So, in order to meet today’s needs LEDs must be thoroughly evaluated. This is done using standardized and uniform LED testing methodologies. The LM-79 testing standard was developed by the Illuminating Engineering Society of North America, commonly known as IESNA.

It was to offer more trustworthy results when evaluating such technologies. It’s worth noting that the LM-79 standard only applies to whole LED bulbs or luminaires. The purpose of this article is to explain how an integrating sphere works

One of the most significant operations in photometry is determining radiant power or luminous flux from light sources using integrating spheres. The integrating sphere is a hollow sphere with a diffusely reflecting substance on its interior surface that provides perfect integration and mixing of light radiation. This is then sent to a detector port for analysis.

Integrating Sphere

The integrating sphere is also called a lumen sphere. It is a hollow sphere with a high reflectivity surface that is used to test lumen, dominant wavelength, chromaticity coordinates, and peak wavelength for light sources and luminaries.

To measure the light from single LEDs as well as LED lighting equipment, the integrating sphere is utilized in conjunction with a spectroradiometer. To ensure LED efficiency and efficacy, photometric, colorimetric, and electrical attributes must be verified. This can be done properly with the help of an integrating sphere.

Workings of Integrating Sphere

A light source is placed in front of the entrance of the sphere, or within the integrating sphere. This is done to catch the complete radiant flux and take an irradiance measurement.

Light beams will bounce multiple times on the reflecting coating in each of these measurement settings. This results in a uniform light distribution throughout the integrating sphere. A baffle reflects a small portion of the light that the detector collects.

Measurement geometries of an integrating sphere

Luminous flux is calculated in several measuring geometries based on lamp type.

4π geometry

The luminous flux of all-round radiating light sources is calculated using this method. The light source is centered on the integrating sphere for this purpose. All radiation emitted in all directions is caught.

2π geometry

The light source in this method is on the sphere wall. This design is only suited for light sources that do not emit back radiation, such as LEDs.

Specifications

The sphere integration system’s painting material complies with CIE. BaSO4 coating is used to paint the sphere walls. Multiple reflections in a fine diffuse are seen. All test samples can be inserted in the sphere in both up and down directions. Auxiliary lamp position, power cable, and power terminal are all built-in. There is a built-in power cable and socket. It is simple to turn on the lamp under test.

The system also includes two photo detector ports, one optical fiber port, and a temperature sensor hole. Integrated spheres are traditionally made up of numerous components. To make the combined spheres LISUN developed A Molding Technology.

A built-in cross laser can assist in installing the standard lamp and the lamp under test at the center of the optical sphere. This makes the test result more accurate.

LED Spheres

Integrating sphere photometers are used to measure the total light flux from lamps, LEDs, and luminaires. Integrating sphere photometers capture the total flux from a light source in lumens for higher accuracy with narrowband sources like LEDs.

An integrating sphere spectroradiometer, on the other hand, is required to examine the spectrum power, chromaticity, or color rendering of a light source.

Calibration

It is fairly simple to calibrate integrating sphere photometers, especially those offered by LISUN. Initially, the conventional lamp is installed in the integrated sphere’s center. The standard lamp is then turned on using the calibrating current.

The integrated sphere is then closed, and the calibration procedure according to the LISUN LMS-9000C Software commences.

The instrumentation used must be calibrated to ensure the necessary level of reliability. A calibration is required for any measurement system that includes an integrated sphere and a spectrometer. A reference lamp with known spectrum distribution and luminous flux values serves as the calibration source.

Certified laboratories calibrate these light sources by measuring the spectrum distribution and luminous flux of a reference lamp using an ideal black body radiator and a monochromator as a reference. The manufacturer calibrates measurement settings on a regular basis, which should be done every 12 months.

Steps involved in calibrating spectrometers

When measuring white LEDs with a prominent blue component in their light, it is generally advised that a similar LED be used for absolute calibration. This is because the blue spectral component in halogen lamps amounts for only about 10% of the energy available along an 800 nm wavelength. This should eliminate any calibration issues that may arise when using a white LED with dispersed light.

However, devices with optical stray light reduction that are utilized in high-quality spectroradiometers are exempt from this requirement. Calibration mistakes caused by stray light can be safely avoided by using appropriate filters and mathematical models.

Advantages

The integrating sphere system is ideal for determining the overall luminous flux and color of small LED luminaires and integrated LED lights. This method has the advantage of allowing for quick estimations while also avoiding the need for a drab atmosphere.

Temperature variations in a temperature-controlled room have no effect on the temperature inside the circle because air development is limited.

Where can the Integrating Spheres be used?

Integrating Spheres are often used to calibrate light output measurements and to measure the light output of LEDs. In cameras, the integrating sphere acts as a homogeneous light source.

When used together with a photodetector, it can measure the total geometric reflux emerging from a light source as well as the flux density of illuminated areas. The light source’s spectral characteristics aid in the selection of an appropriate photodetection system.

It is also utilized to measure high-power laser sources. This is because the proportion of flux received by a photo-detector positioned on the spherical surface is almost equal to the product of fractional surface area consumed by its active area.

It can also be used to figure out how powerful industrial CO2 lasers are. It can also determine the transmission and reflection qualities of objects.

When an object is positioned at the integrating sphere’s entrance port with a light source behind it, the transmitted light bounces off the reflecting covering and is collected by the detector.

The same measurement can be made by removing the item and measuring the light source’s output flux directly, then calculating the transmittance. Alternatively, you can determine the object’s reflectance by positioning it diagonally across from the entrance port.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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Tags：LPCE-2(LMS-9000) , LPCE-3