Gonio photometric procedure for light measurement

A Goniophotometer is a device used for measuring the light emitted from an object at multiple angles. Goniophotometers can measure the properties of light that are emitted by a light source. They have been used frequently for the last few years with the increase in advancements. LED light sources have been introduced in the last few years. These are mostly directed light sources, and light is not distributed homogeneously. LEDs tend to direct the light in a certain direction, which is called a Lambertian source.

A goniophotometer is basically used for
• Measurement of the luminous flux of any light source
• Measurement of luminous intensity distribution from any light source
• Measurement of correlated color temperature
• Measurement of color uniformity

Measurement with Goniophotometer

Measurement of luminous flux 
A laser gives a very high amount of luminous flux in 1 small spot but hardly to no luminous flux at all in any other direction. An old lightbulb is different because it sends out the same amount of luminous flux in any direction.

Measurement of Luminous Intensity
A directed light can give a very high amount of luminous intensity from a certain angle. On the other hand, it gives almost none from a slightly different angle.

Measurement of Color Uniformity
When light is measured from different angles, and different distances, the properties of the light can change. A high color uniformity means that the color temperature is evenly spread throughout the different angles. A low color uniformity means that the color temperature differs greatly with the different angles. A regular light bulb spreads the light out in an almost homogenous radial distribution, sending out light almost at the same intensity in all directions.

Goniometer for light measurement

The goniophotometer is within the automotive industry used to determine the type of light from a headlight to comply with the regulations.
The luminous intensity distribution is one of the most fundamental characteristics of luminaries.

A goniophotometer is usually used to measure the emitted light. The whole setup features a mechanical goniophotometer with a horizontal and vertical axis. These axes are for the rotation of the test sample and a photometer for the measurement of luminous intensity.

The luminous intensity and specific measuring planes comprise several curves. The distribution of these curves depends on the light source and type of goniophotometer. According to the measuring planes, goniophotometers are divided into three types. These types are classified as A, B, and C . All these types are optronic line core products and are subject to continuous improvements.

Types of Goniophotometers

As already discussed, there are 3 types of goniophotometers. We have described the specific details of each type of goniophotometer here.

Type A Goniophotometer
• Fixed horizontal axis
• Measurements are performed by the rotation of the sample around the horizontal axis
• The position of the second axis is fixed at one
• Type A goniophotometer is used for automotive lighting and multiple other-directed light sources
• Double Column structure

Type B Goniophotometer
• Fixed Vertical Axis along with an attachment of horizontal axis
• Both axes are in a perpendicular direction to the main output direction of the light source
• Double column structure
• B- β coordinate system and A- α coordinate system

Type C Goniophotometer
• Fixed Vertical Axis in a perpendicular direction to the line of measurement
• A horizontal axis in a parallel direction to the main output direction
• Single Column structure
• Applied to fixed tube lamps, spot lamps, and other devices

Units of measurement

A goniophotometer can measure the distribution and properties of light in different units. These units are light intensity (candela), light level (lux), and brightness (cd/m2).

Gonio photometric Procedure for Measurement of light intensity

It is possible to do calculations for measuring the lumen value of any light source by having accurate data. Light intensity values ​​for a light source are calculated at different angles. These values ​​are used to find the total output of the light means lumen. If we measure the lumen in this way, its accuracy would be high.

It is necessary to take the test in a dark room. You can determine the room’s requirements by the size of the device. It is important to consider the room size, wall paint, and room temperature of the room for goniophotometer measurement. If the darkroom is not capable of meeting the test specifications, the measurement will not be correct.

The temperature should be 25 degrees Celsius. You can also change the room size according to the lamp being tested. You can paint the wall black, and it will not create any reflection.

Methods for measurement of Light Intensity

A goniophotometer is workable in a larger darkroom. Reflected light should not enter the probe. This is achieved by using the low-reflectivity materials in the room. The integral illuminance method and the luminous intensity integral method measure the light intensity.

Illuminance integral method
The measuring distance is not limited, while the measurement space is not too large. An accurate total luminous flux is only achieved when the distance is small. In this way, we can measure the illuminance.

Light intensity integration method
This method is used to calculate the total luminous flux. This is achieved by measuring the light intensity distribution of the light source in the space and integrating the entire space. A small distance is required to measure the light intensity distribution. The measured object can be considered a light source. We can calculate the light intensity by multiplying the distance with the inverse square.

LSG-6000 Goniophotometer

What is the use of a goniophotometer?

LISUN manufactures an LSG-6000 goniophotometer. It can measure all the lighting sources, LED, Plant Lighting, or HID luminaires such as indoor and outdoor luminaires, roadway luminaires, street lamps, floodlights, and other kinds of luminaires.

Measurement
• Luminous Intensity Data
• Photometric Data
• Luminous Intensity Distribution
• Zonal Luminous Flux
• Luminaries Efficiency
• Luminance Distribution
• Coefficient Of Utilization
• Luminance Limitation Curves Glare
• Maximum Ratio of Distance to Height
• Equal Illuminance Diagrams
• Curves of Luminaires VS Lighting Area
• Isocandela Diagrams
• Efficient Luminescence Angle
• EEI, UGR, etc.

Frequently Asked Questions

What is the function of the goniophotometer?

A goniophotometer is considered a photometric device. It is used to measure the perceived power of a light source at different angles.

What does a goniophotometer measure?

A goniophotometer is a photometric device used to measure light sources’ light at different angles.

What are the different types of goniophotometers?

Universal Goniometer is available in two forms: short arm and long arm. We use the short arm goniometer for smaller joints like the wrist, elbow, or ankle,
• Twin Axis Electro goniometer 
• Gravity Goniometer/Inclinometer. 
• Software/Smartphone-based Goniometer.
• Arthrodial Goniometer

How can we define the total luminous flux?

Luminous flux (in lumens) is defined as the measure of the total amount of light a lamp puts out. The luminous intensity (in candelas) is defined as the measure of how bright the beam in a particular direction is.

How does the goniophotometer mirror work?

Goniophotometer works according to the measuring principle of the fixed detector and rotating lamp method. We install the measuring lamp on a two-dimensional rotating work table. The luminous center of the lamp touches the rotating work table’s rotating center through the help of the laser beam of the laser sight.

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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