The most critical factor that affects the quality of lighting is the luminous distribution performance of lamps. Using scientific testing methods and selecting the appropriate test instrument is the basis of obtaining accurate luminous distribution properties of luminaires. The test of luminaires’ luminous distribution is an important part of luminaire design and lighting design for quality control. Especially with the development of new sources and new lighting technology, it presents new challenges for the test of luminaire luminous distribution. Thus, Lisun has developed various goniophotometers which adopting different test methods for testing luminous distribution.
1) Moving Detector Goniophotometer
The method of goniophotometer to test total luminous flux is spectrophotometry. The principle is to test the luminous intensity of light source at different directions (or the illumination at a given distance from the light source), and then to calculate the total luminous flux by the data of luminous intensity in many different directions. According to LM-79 Clause 9.3.1 standard, only type C goniophotometer with moving detector can be accepted. In this kind of goniophotometer, the photometer head is fixed, and is located in the optical axis line. During the measurement, the lamp just need to do spin motion, and the mirror rotates around the tested luminaire, and reflecting the optical signal into the detector. The tested light source and the normal of photo detector enter into a certain cone angle. Therefore, the movement airflow has less impact on the lamp temperature for this kind of goniophotometers.
During the test, the tested lamp will keep burning position and be fixed, near field detector move together with the big mirror in a line, and the far field detector will move with the big mirror synchronously. The detector will always sense the light directly from the luminaries. Lisun LSG-3000 Moving Detector Goniophotometer is full meet LM-79 Clause 9.3.1 request. It is more applied in North America, mainly used in large-scale experimental laboratory or third party testing organization. Its working principle is shown as Figure 1.
Lisun LSG-1800B/LSG-1700B/LSG-1600B High Precision Rotation Luminaries Goniophotometer carries out measuring methods of fixed location and rotating luminaries. It can work by double pillars structure and single pillar structure to realize C-γ, A-α and B-β measurement solution, it fully meets CIE, IEC, LM-79, GB etc standards. LSG-1800B adopts Japanese Mitsubishi Motor and German Angle encoder System to keep the test accuracy to 0.0017degree. It is widely used in optical industry laboratory. It is used to test for LED street luminaries, indoor luminaries and mining luminaries’ photoelectric parameters.
The detector of this kind of goniophotometer is fixed at a certain distance from the lamp, and lamp is mounted on a turntable which can be rotated on horizontal and vertical direction. The main vertical axis of the turntable is fixed, and the horizontal axis can be moved. Under the control of computer, the motor drives the vertical axis to rotate, and the photo detector will test lamp’s luminous intensity values in the different direction on the horizontal plane. When the measurement on a plane is completed, the motor of horizontal axis will drive lamps to turn at an angle, and then the photo detector will measure the luminous intensity distribution on another plane. So as the repeated progress, the vertical axis continuously rotating, and horizontal axis intermittently move, to achieve the measurement of light intensity distribution data in all directions of space. Since this kind of goniophotometer will continuously rotate and change the status of luminaries, it is not suitable for gas discharge lamps etc. whose photo and electrical parameters will be easily influenced by its working conditions. However, it is more suitable for grille lamps testing, and mainly for LED lighting manufacturers and retailers to measure the quality of the lamps.
3) Goniophotometer for Automotive and Signal Lamps
For road lighting photometric test, the current street light is mostly gas discharge lamp. According to CIE and FMVSS108 standard requirement, for the measurement of gas discharge lamps, it requires that luminaires can not be overturned. Thus, we generally use goniophotometer with moving mirror to do the test. LSG-1950 is the CIE A-α goniophotometer. It is mainly used to measure transportation industry luminaries such as traffic signal lamp, public transport, train and space ship luminaries. The photometer head keeps static and faces to the teat sample while the test samples rotates around both horizontal axis and vertical axis, so the luminous intensity and illuminance of the tested lamp or luminaires can be tested.
Goniophotometer is a large precision optical test equipment, while its measurement is a very professional work. The test equipment, laboratory construction and operating personnel is three important aspects of affecting the measurement results. On test equipment selection, we must consider the properties of the beam of lamps, especially the measurement of street lights and other outdoor lighting. And testing methods must comply with CIE far-field photometry principles, with particular attention to stray light impact of test equipment and laboratories. To ensure the accuracy of test results, in all aspects of the test equipment, we should properly place the corresponding diaphragm to eliminate stray light.