Goniophotometer as an Instrument for Measuring Light Intensity

The strength or quantity of light that a light source can produce is known as light intensity. The light intensity is the amount of power produced by the light source. Its measurement unit is the Candela or Cd. A particular measurement equipment is required to determine this intensity. One such instrument is the Goniophotometer. This article will see how a goniophotometer can be used as an instrument to measure light intensity.

Goniophotometer

A goniophotometer is a device that changes the position of a photometer or goniometer at a well specified geometry. This is done to measure light distribution in terms of light intensity or illuminance distribution of a light source or surface. A basic goniophotometer is made up of a mechanical device that supports the luminaire to be measured and a photometer or spectroradiometer that allows them to be moved about to generate a circular locus.

It is a device that uses a mirror to reflect light from a source at various angles. At those angles, measurements are conducted to determine how the light radiates from the source. The goniophotometer also creates an IES file that contains information on the spatial distribution of light. The lighting layouts can then be created using that file.

The total luminous flux, spectral radiant flux, and color quantities can be calculated using optical data from the defined angle of spectral irradiance.

Type-C Goniophotometer

Rotating lamps, rotating detectors, and fixed lamps are the three major types of goniophotometers. LISUN produces LSG-6000 that is a mirror type-C goniophotometer. It is also known as a moving detector goniophotometer.

The LSG-6000 is an automatic light intensity testing device for measuring light. It has been enhanced from the LSG-5000 and LSG-3000 to meet the requirements of the LM-79-19 standard. The measuring distance varies between 5 and 30 meters.

Where to use a Goniophotometer?

The goniophotometer is a device that is used to examine the performance of light equipment in the lighting and automotive industries. The goniophotometer is also used to measure the light from traffic signal lamps. The device can be used to assess the reflectiveness of traffic signs and other reflective materials.

International Standards

The LSG-6000 Moving Detector Goniophotometer was formed according to international standards. The IESNA and CIE working principles are followed by LISUN instruments. It fully complies with the standards of 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 of the LM-79-19, IES LM-80-08, COMMISSION DELE.

Instrument for Measuring Light Intensity

The goniophotometer can measure the light intensity of all forms of lighting sources. These include indoor and outdoor luminaires, roadway luminaires, street lamps, flood lights, and LED lighting. Goniophotometers can measure various features of these devices. One such measurement is light intensity.

How to Measure Light Intensity?

The goniophotometer uses a fixed detector and revolving lamp approach to measure the light. The measuring lamp is fixed on a two-dimensional rotating worktable. The laser sight’s laser beam aligns the luminous center of the lamp with the rotating center of the spinning worktable.

The luminaire revolves around the vertical axis when it is lit. The reflector rotates around the horizontal axis and the synchronization axis rotates in the opposite direction. The synchronized rotation of the luminaire and the reflector can be measured at any horizontal or vertical angle.

This can be done without tilting the luminaire. The detector is positioned in front of the reflector with a limited metering distance to collect light from all directions. The light intensity is calculated based on the distance between the light source and the detector after measuring the illuminance value.

The LISUN goniophotometer program supports the export of CIE, IES, LDT, and other file formats. Other illumination and luminaire design applications can use these types of format files as well.

Methods to Measure Light Intensity

A goniophotometer will be needed to work in a larger darkroom. Reflected light entering the probe should be avoided. This is done by using low-reflectivity materials in the room. The illuminance integral method and the luminous intensity integral method can be employed to measure light intensity, depending on the layout of the measuring light path.

Illuminance integral method

The measuring distance is unlimited and the needed measurement space is little. An accurate total luminous flux can be achieved even if the distance is small. This is as long as the illuminance can be measured.

Light intensity integration method

The goniophotometer’s light intensity integration method calculates the total luminous flux. This is done by measuring the light intensity distribution of the light source in the space and integrating the entire space. A suitable distance is necessary to measure the light intensity distribution. The measured object can be thought of as a point light source. The light intensity can be calculated by multiplying the distance by the inverse square.

Conditions to Properly Measure Light Intensity

The goniophotometer tests should be performed in a dark room. The maker of the test gadget determines the room’s criteria. Goniophotometer measures include some critical factors. These include the size of the room, the color of the walls, and the temperature. Measurement errors might occur if the darkroom does not fulfill the manufacturer’s requirements.

The ambient temperature should be 25°C to perform the test properly. The size of the room can be adjusted. It depends on the light type being tested and the test device. The room’s walls should be painted in a flat black paint with no reflective properties.

Following the measurement of light intensity, LDT (EULUMDAT) and IES files are created. By transferring these files to software, lighting simulations can be performed.

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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