Goniophotometric testing for LED lighting

Background theory
You may use various photometric parameters to assess light sources through a goniophotometer, including the light flow, luminous intensity, and spectrum distribution. Luminous flow (measured by lumens) is a source’s total light output and is the basic photometric amount by which other quantities like luminous intensity are determined. There is a must-use of the best goniophotometer for goniophotometric testing. The spectral distribution or spectral composition specifies the relative amounts of each wavelength or color consisting of a light source.

Test setup
The values ​​​​​​​​​​​​​for the luminous flux of every LED product are acquired using a Type C goniophotometer for measuring the luminous intensity distribution. The goniophotometer is a motor-driven arm photometer that spins in-plane and at a set distance from the light source to be measured. Lux (lm/m2) values ​​​​​​​​​​​​are recorded into our custom application at each angular step in synchronization with motor actuation.

The scanning resolution in our test setup is a 1.8° (vertical) and 90° (horizontal) longitudinal grid. The precise angle resolution in the vertical plane was utilized to reduce the effect on a vast data collection of any non-systematic measurement errors. A 90° lateral resolution was adequate for symmetrical distribution testing luminaires.

Since our testing focuses on interior LED light fixtures, light is usually transmitted forward, and the test equipment did not impede the light emission. The test was performed in a dark and temperature-controlled environment to prevent ambient light and temperature fluctuation from affecting the findings.

The goniophotometer enables us to measure the LED light output on two transverse planes along a circumferential region. An interpolation and integration procedure is computed based on our data. The entire light output is derived across a spherical surface, regardless of the measurement distance, ie, light flow.

Procedure
For goniophotometer testing of road lighting, the majority of the existing street lights are gas discharge lamps. According to the CIE and FMVSS108 standards, it is necessary that luminaires cannot be toppled to conduct measurements on gas discharge lamps. We thus do the test with a goniophotometer with a moving mirror in the majority of cases. Therefore, LISUN has the best devices for goniophotometric testing.

It is mainly used to measure luminaries in the transportation sector, such as traffic signal lamps, public transit, railway, and space ship luminaries. During testing, the photometer head remains stationary. It faces the teat sample while the test samples spin along both the horizontal and vertical axes, allowing for measuring the luminous intensity and illuminance of the tested lamp or luminaire.

Importance of goniophotometer
In addition to being large precision optical test equipment, the goniophotometer’s measurement represents a high level of professionalism. The test equipment, laboratory construction, and operational staff are all significant factors that influence the outcome of the measurements. When selecting test equipment, we must consider the characteristics of the lamp’s beam, which is particularly important when measuring street lights and other outdoor illumination.

Furthermore, testing techniques must adhere to the rules of CIE far-field photometry, with particular consideration paid to the effect of stray light on test equipment and labs. To guarantee the accuracy of test results, we must ensure that the matching diaphragm is correctly placed in all parts of the test equipment to minimize stray light.

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, 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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