Goniospectrophotometer：luminous intensity measuring device

Goniophotometer is also know as luminous intensity measuring device, is divided into vertical goniophotometers and horizontal goniophotometers. Goniophotometer is the main measuring equipment for light distribution performance test of lamps, which can be used to measure parameters such as spatial light intensity distribution, total luminous flux and lamp efficiency of lamps or light sources. The composition of the goniophotometer system includes: precision turntable and control system, spectral analysis system, standard lamp, alignment system, computer processing system and other parts.

LM-79 Moving Detector Goniophotometer (Mirror Type C)

The goniophotometer needs to be used with a larger dark room, use low reflectivity materials in the room to avoid reflected light from 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.

Depending on the arrangement of the measuring light path, two measurement schemes can be used to measure the luminous flux: the illuminance integration method and the 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 with a compact goniophotometer, by measuring the illuminance distribution of the light source in space, and integrating the whole space to obtain the total luminous flux.
Because it is not sensitive 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 realize the benchmark unit of luminous flux.

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 the distribution of light intensity requires a sufficient distance, and the measured object can be approximately regarded as a point light source, and the light intensity can be measured using the inverse square relationship of the distance.
Goniophotometers are mainly divided into several types: lamp rotating type, detector rotating type, and lamp fixed type.

working principle:
Luminous intensity can be obtained by rotating the lighting device in different directions at a fixed distance for illuminance (far-field) or illuminance (near-field) measurements. With sufficient angular steps and ranges, the luminous flux of a luminaire can be calculated by summing all luminous intensities in each measurement direction. A goniometer is an instrument with an axis of rotation for measuring the luminous flux and luminous intensity distribution of a lighting device or light source.

From the luminous intensity distribution, properties of the lighting application, such as lateral/longitudinal isolux curves or conic diagrams, can be deduced. 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 And class C, the difference is as follows:

Class A is suitable for automotive lighting that characterizes relatively limited light beams. Type A goniometers have a fixed horizontal axis and a moving axis perpendicular to the central axis. Measurements are made 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 monitors and floodlights. Type 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. Type 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 on the conical surface. Type C goniometers are the same as Type B except that the light source is rotated by 90°.

1. Definition of light distribution curve:
The light distribution curve is also called the luminous intensity distribution curve. In fact, it is a curve that shows 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 important thing is to record the light intensity of the lamps in all directions.

2. Classification of light distribution curve:
According to its symmetry, the light distribution curve can usually be divided into: axial symmetry, symmetry and asymmetric light distribution.
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. the
Symmetry: When the light distribution of the c0° and c180° sections of the lamp is symmetrical, and the light distribution of the c90° and c270° sections is symmetrical, such a light distribution curve is called a symmetrical light distribution.
Asymmetry: It refers to the asymmetric light distribution of any section of c0°-180° and c90°-270°. the
According to the beam angle, the light distribution curve can usually be divided into:
Narrow light distribution (< 20°)
Medium light distribution (20°> 40°)
Wide light distribution (> 40°)
In fact, there is no strict definition. The definitions of wide, medium and narrow are slightly different for each manufacturer.

There are usually two ways to express the light distribution curve test:
Polar notation
The Chinese method is usually used to describe the light distribution of indoor and road luminaires. It is very vivid to represent the light center of the lamp with the origin of polar coordinates, the magnitude of the intensity with a vector in a certain direction, and the angle between the light intensity vector and the optical axis with the angle of polar coordinates:

Cartesian coordinate notation:
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.

What is the definition of type C goniophotometer?

LSG-6000 Moving Detector Goniophotometer (Mirror Type C) was manufactured by LISUN completely meets LM-79-19, IES LM-80-08, COMMISSION DELEGATED REGULATION (EU) 2019/2015, CIE-121, CIE S025, SASO 2902, IS16106 and EN13032-1 clause 6.1.1.3 type 4 requirements. LSG-6000 is the latest upgraded product of LSG-5000 and LSG-3000 in compliance with the requirements of the LM-79-19 standard Clause 7.3.1, its an automatic light distribution intensity 3D curve testing system for measuring light. The darkroom can be designed according to the customer’s existing room size.

LM-79 Moving Detector Goniophotometer (Mirror Type C) 

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.

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