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Goniophotometer is divided into vertical goniophotometer and horizontal goniophotometer. Goniophotometer is the main measurement equipment for testing the light distribution performance of lamps. It can be used to measure parameters such as spatial light intensity distribution, total luminous flux and lamp efficiency of lamps or light sources. The goniophotometer system consists of: precision turntable and control system, spectrum analysis system, standard lamp, alignment system, computer processing system, etc.
Goniophotometer needs to be used in a larger dark room, use low reflectivity materials in the room to avoid reflected light entering the probe. Since the measurement system is easily affected by the ambient temperature, it is very critical to keep the temperature of the light source itself stable. The goniophotometer takes readings angle by angle, which is very time consuming. If you only need to measure the luminous flux parameters of the lamp, there is no strict requirement on the measurement distance.
According to the arrangement of the measurement light path, two measurement schemes can be used to measure the luminous flux: illuminance integration method and light intensity integration method:
1. Illuminance integral method. There is no limit to the measuring distance and less measuring space is required. As long as the illuminance can be measured, accurate total luminous flux can be obtained even at short distances. It can be measured using a compact goniophotometer, which measures the illumination distribution of the light source in space and integrates the entire space to obtain the total luminous flux. Because it is insensitive to the measurement distance and the installation position of the light source, and can avoid the use of reflectors, it can achieve high measurement accuracy. It is the method recommended by CIE to achieve the luminous flux reference unit.
2. Integral method of light intensity. The light intensity integration method measures the light intensity distribution of the light source in space and integrates the entire space to obtain the total luminous flux. Measuring light intensity distribution requires sufficient distance. The object to be measured can be approximately regarded as a point light source, and the light intensity can be measured using the inverse square distance relationship.
Goniophotometers are mainly divided into several types: lamp rotating type, detector rotating type, and lamp fixed type.
How it works:
Luminous intensity can be obtained by measuring illuminance (far field) or illuminance (near field) by rotating the lighting device in different directions at a fixed distance. With sufficient angular step size and range, the luminous flux of a lighting device can be calculated by summing all luminous intensities in each measurement direction. A goniometer is an instrument with a rotating axis used to measure the luminous flux and luminous intensity distribution of a lighting device or light source.
According to the distribution of luminous intensity, properties of the lighting application can be inferred, such as lateral/vertical iso-illuminance curves or cone diagrams. According to the way the lighting equipment is rotated during the measurement process and the photometric data system obtained during this measurement process, the types of goniometers can basically be divided into Group 1, Group 2 and Group 3, also known as Type A, Type B The difference between Category C and Category C is as follows:
Class A is suitable for characterizing automotive lighting with a relatively limited beam. Type A goniometers have a fixed horizontal axis and a moving axis perpendicular to the ** axis. Measurements are taken by rotating the light source around a horizontal axis while keeping the other axis in a fixed position (rotation vs height).
Class B is suitable for displays and floodlights. Class B goniometers have a fixed vertical axis and a moving horizontal axis. Measurements are made by rotating the light source around a vertical axis while keeping the other axis in a fixed position (height vs rotation).
Class C is suitable for general lighting systems. Class C goniometers are a highly specialized type with a fixed vertical axis and a moving horizontal axis. Measurements are made on the C-plane or cone surface. Type C goniometer is the same as Type B except that the light source is rotated 90°.
Definition of light distribution curve:
1. The light distribution curve is also called the luminous intensity distribution curve. In fact, it is a curve that expresses the distribution of light emitted by a lamp or light source in space. It can record the luminous flux of the lamp, the number of light sources, the power, the power factor, the size of the lamp, and the efficiency of the lamp, including the manufacturer and model of the lamp. Of course, the most critical thing is to record the light intensity of the lamp in all directions.
2. Classification of light distribution curve:
Light distribution curves can usually be divided into: axial symmetry, symmetry and asymmetric light distribution according to their symmetry properties.
Axial symmetry: Also known as rotational symmetry, it means that the light distribution curves in all directions are basically symmetrical, and the general downlights and high bay lights have such a light distribution.
Symmetry: When the light distribution of c0° and c180° sections of the lamp is symmetrical, and the light distribution of c90° and c270° sections is symmetrical, such a light distribution curve is called symmetrical light distribution
Asymmetry: refers to the asymmetric light distribution in any of the c0°-180° and c90°-270° sections.
The light distribution curve can usually be divided into:
according to its beam angle.
Narrow light distribution (< 20°)
Medium light distribution (20°>40°)
Wide light distribution (> 40°)
In fact, there is no strict definition. Each manufacturer has slightly different definitions of wide, medium, and narrow.
There are usually two ways to express the light distribution curve test:
Polar coordinate representation:
The Chinese method is usually used to describe the light distribution of indoor and road luminaires. It vividly sits on the poleThe origin of the mark represents the light center of the lamp, the intensity is represented by a vector in a certain direction, and the angle between the light intensity vector and the optical axis is represented by the angle of polar coordinates.
Cartesian coordinate representation:
This method is typically used to describe the distribution of light from floodlights and luminaires and sources with very narrow distributions. The origin of rectangular coordinates is used to represent the light center, the abscissa is used to represent the direction angle, and the ordinate is used to represent the light intensity.
LSG-6000 rotating probe vertical goniophotometer (full space goniophotometer) fully meets the requirements of LM-79-19, EN13032-1 clause 6.1.1.3 goniophotometer type 4, CIE S025, SASO2902, IS16106 and GB etc. Regarding the requirements for optical parameter testing. LSG-6000 is the latest upgraded product of LSG-5000 and LSG-3000 in response to the requirements of Clause 7.3.1 of the LM-79-19 standard. It can automatically test 3D light intensity distribution curves, and the test distance can be designed according to customer needs. It can meet the test requirements of various light sources, such as LED light source, plant lighting, HID light source, indoor and outdoor lighting, street light and flood light, etc.
LM-79 Vertical Goniophotometer System LSG 6000
