Integrating Sphere: Introduction & Cost Effective Solutions

As an emerging light source, LED is very different from the traditional light source in terms of its own structure and luminous characteristics. Due to the self -absorption effect of the LED itself and the measurement error brought by the internal shield of the integrating sphere, the LED’s optical flux error is measured with a large amount of optical flux errors. The position and gear screen of the internal light source in the traditional integrating sphere should be adjusted to reduce the measuring error. The data and theoretical calculation of software simulation proves that LEDs should be placed on the inner wall of the integrating sphere and 90 ° in the same plane as the detector probe.

The difficulty of the light source of the light source is the test of the optical flux. Compared with traditional light sources, due to the particularity of LEDs, although the International Lighting Commission (CIE) and the measurement research institutions of the United States, Canada and other countries have proposed the test method of LED optical flux, it has not been recognized internationally to this day Simple test method with similar optical flux test methods.

The existing LED optical flux test methods exist, including: ① The use of optical battery detectors can not achieve the accurate matching of LED function V (λ) at all spectral points, especially the existing detectors in blue and red wave bands are large. Causes test errors [1]; ② Place the optical flux test method of traditional light sources in the integrating sphere. Because the Test LED integrating sphere are generally small, even only 5cm in diameter, the integrating sphere theory will not be satisfied, resulting in testing, which will cause testing, which will cause testing. Principle error [2]; ③ If the standard light is placed on the inner surface of the integrating sphere, the conventional standard lights that emit light in all directions will not be used, and the LED standard light is difficult to achieve spectral standards [2]. The above problems have made the test of LED optical flux have not yet been perfected and unified, which has also affected the discrimination of LED performance, which is not conducive to the development of the LED industry. The main problem of this article is the reasonable position of the LED in the integrating sphere device that measures the total light flux of the LED, that is, whether the LED can be placed in the inner wall of the integrating sphere.

According to the particularity of the LED optical flux measurement, the LED measurement is uniquely optimized in the design of the integrating sphere. At the same time, the high reflectivity of the man -reflex material is used, which greatly improves the stability and accuracy of the system. The experimental results show that the stability and consistency of the system are much higher than that of other ordinary LED test systems. It is a system that is really suitable for LED optical parameters.

During the use of the integrating sphere for optical flux measurement, unlike ordinary light sources, the optical flux measurement of LED light sources has challenged the equipment in terms of test accuracy. On the one hand, LEDs are usually stronger than ordinary light sources, and they usually do not light up in the entire space evenly. This feature makes the distribution of LED direct light on the surface of the integrating sphere is not uniformly distributed. The uneven distribution directly leads to different reflection characteristics of direct reflection of different LEDs. Because the position of the detector mouth and the setting of the baffle is fixed, and different reflex distributions are directly manifested as signal fluctuations. In ordinary measuring systems, different positive dispersion angles, different placing directions in the same LED, different positions in the same direction, etc., even if the optical flux is the same, the measured value shows great differences. According to customer verification results, the impact of the placement direction of the general LED measurement system LED often has more than 50% on the optical flux measurement results (the difference between the maximum signal and minimum signal measured by the same LED in different directions).

What is the integrating sphere?

Integrating sphere is a hollow sphere with high reflected inner surface.
It is used to collect or launch a high -efficiency device that is used in the ball or placed in the sphere or placed outside the sphere and near a window. The small window on the sphere can make the light enter and get close to the detector.

Integrating sphere working principle and application:

Test of the light color parameters used in the integrating sphere and the spectrometer for light source:
The CIE S025 / E: 2015 standard and EN 13032-4: 2015 described by the IESNA LM 79 stipulate that the size of the sphere must be 10 times larger than the size of the lamp [2] [3]. This is not suitable for linear lights with a small total area of the shell. On the other hand, the practical principles adopted by many internal measurement laboratories can measure the lamp with a size of 30 % in the sphere diameter. For details, please refer to the following articles: Practical techniques for LED measurement on the integrating sphere and angle metering instrument based on CIE025 [4]. Remember that each element that introduces the integrating sphere will interfere with measurement (therefore limits the possibility of multiple reflections) and absorb part of the light flux. By placing auxiliary light sources in the sphere, this impact can be compensated to determine the absorption coefficient. If we want to establish a certification laboratory in the future, we must consider advice on applicable standards. For the quality control of the factory, you can use your own regulations, but you must consider the error caused by the size of the lamp in the sphere.

The integrating sphere works with a Spectroradiometer to do the photometry, colorimetry and radiometry parameters measurement.
• IS-0.3M/IS-0.5M is for LEDs, LED modules, mini LED bulbs & other small lamps. The flux testing range is 0.001 to 1,999 lm
• IS-1.0MA is for CFL or LED bulbs. The flux testing range is 0.1 to 199,990 lm
• IS-1.5MA/IS-1.75MA is for CFL, LED bulb and tube, fluorescent lamp, CCFL. The flux testing range is 0.1 to 1,999,900 lm
• IS-2.0MA is for HID lamps or high power lamps. The flux testing range is 0.1 to 1,999,900lm

Notes for the integrating sphere:

1. Points of the integrating sphere must be high enough, cover the wide wavelength range, reliable and stable performance, good material uniformity, and consistent performance (for the result of the measurement of strong light sources such as LED, the optical flux error should be less than ± 3% ), The stable spectral reflectance characteristics, the coatings are durable, do not fall off, are not easy to turn yellow, and are easy to clean up. It can ensure the reliable service life of at least 10 years.

2. The integrating sphere system must be calibrated by the standard lights. Standard lights must have high stability and high repetitiveness. They must be screened, aging and calibrated under the recommendation guidance of IESNA to ensure that its ZUI is high -precision and traceable to NIST.

3. The sphere is more sensitive to the sphere, and the self -absorption effect is more sensitive. Usually the size and shape of the lamp measurement are not consistent with the size and shape of the standard lamp. The integrating sphere system must install and absorb standard lights for self -absorption correction. During the entire self -absorbing measurement process of absorbing standard lights, the amount of light radiation must be stable.

LPCE-2 Integrating Sphere Spectroradiometer LED Testing System is for single LEDs and LED lighting products light measurement. LED’s quality should be tested by checking its photometric, colorimetric and electrical parameters. According to CIE 177, CIE84,  CIE-13.3, IES LM-79-19, Optical-Engineering-49-3-033602, COMMISSION DELEGATED REGULATION (EU) 2019/2015, IESNA LM-63-2, IES-LM-80 and ANSI-C78.377, it recommends to using an array spectroradiometer with an integrating sphere to test SSL products.

But if your budget is limited. LISUN LPCE-3 is a CCD Spectroradiometer Integrating Sphere Compact System for LED Testing. It is suitable for single LED and LED luminaires’ photometric, colorimetric and electrical measurement. The measured data meets the requirements of CIE 177, CIE84,  CIE-13.3, COMMISSION DELEGATED REGULATION (EU) 2019/2015, IES LM-79-19, Optical-Engineering-49-3-033602, IESNA LM-63-2, ANSI-C78.377 and GB standards

Tags：LPCE-2(LMS-9000) , LPCE-3