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LED measurement: How we measure

Standards:

  • Traceable to NIST/PTB calibration standards
  • CIE Publ. 127 and 127-2, measurement of LED’s



As one of few providers, we are able to measure per CIE Publ. 127 and 127-2. A multitude of brackets enables us to measure very small, as well as very large LED’s.

The LED measuring system by Optronic is made up of various high quality components:

OL 770-LED High-Speed spectroradiometer, OL 15AB illumination tube, OL 700-30 LED-Goniometer, OL IS-1800 Integrating sphere.


OL770 High-Speed Spectroradiometer

With its accessory components, the high speed spectroradiometer measuring system is designed for light emitting diodes (LED's). Per the manufacturer, the central multi-channel spectroradiometer is currently the fasted and also the most accurate measurement acquisition system.

The following data can be processed:

  • Spectral radiant flux (Watt/nm)
  • Radiant flux (Watt)
  • Luminous flux (Lumen)
  • Dominant wave length
  • Peak wave length
  • Spectral full width at half maximum
  • Colour saturation
  • Colour temperature
  • Colour rendering indexes
  • Colour coordinates
  • LED radiant intensities (Watt/sr)

Illumination Tube

Per the manufacturer, the OL 15AB LED illumination tube was designed specifically for use with the OL 770-LED high speed spectroradiometer measuring system, to perform fast and exact measurements of the illumination of light emitting diodes (LED’s). The device was developed to capture „Medium LED Illumination“ compatible with CIE Publication 127. The geometry of the illumination tube meets the „Near Field“ requirements of the standardized CIE measuring requirements A and B. The flexible construction allows the acquisition of both CIE measuring requirements A and B in one single set of components. One special feature is the optical fibre/integrating sphere combination unique to this illumination tube, which allows for a homogenous sensitivity and removes key error sources.

Features:

  • CIE Publication 127 and 127-2 compatible
  • Quick and accurate determination of LED illumination
  • Compact design for combined evaluation per requirements A and B
  • Designed specifically for the use of the OL 770-LED high speed spectroradiometer measuring system

Integrating sphere

The LED’s are clamped into the specifically highly reflective coated ball. This is where the spectral spread, the luminous flux, the colour temperature and other LED parameters calculated from the spectral spread, are determined.
Per the manufacturer, the integrating sphere OL IS-1800 is one of the most accurate luminous flux measuring optics on the market. The experience of more than 30 years was incorporated into the design of this optic available as a standard product. This makes it one of the most helpful tools for development, production and quality assurance of lamps and other light sources, especially LED’s. The special concept of the OL IS-1800 integrating sphere allows the type of precision that is required by scientific researchers. The sphere, bezel and critical internal components are coated with the sturdy reflection material OPTOLON 2«. It is a new reflection material which combines a high amount of reflection, being washable and hydrophobic.

We measure the following parameters:

  • Precision reference light concept for utmost accuracy
  • Radiant flux (Watt)
  • Luminous flux (Lumen)
  • Spectral radiant flux (Watt/nm)
  • Dominant wave length
  • Peak wave length
  • Half value width
  • Colour saturation
  • Colour temperature
  • Colour rendition indexes
  • Colour coordinates

Specification
Integrating sphere diameter (standard): 18, 39, & 76 inches
Integrating sphere coating (washable): Optolon 2
Reflection grade (visible area): 98.5%
Maximum lamp output: 150W (18”), 1000 W (39”), & 5000 W (76”)
Maximum lamp length: 12 inches (18”), 30 inches (39”), & 60 inches (76”)
Maximum luminous flux: 140,000 lm (18”) to 500,000 lm (76”)
Minimum luminous flux (noise level): 7x 10-7 lm (18”) to 2.5 x 10-6 lm (76)
Weight (approx.): 50lb. (18”), 106 lb. (39”), & 640 lb. (76”)
Integrating sphere construction: Aluminium (=39” [1 m]) or fibre glass (>39”)
Calibration standards used for spectral radiant flux
Luminous flux (typical): 650lm (45 W) to 5000 lm (200W)
Colour temperature (typical): 2950K (45W) to 3165K (200W) [2856K optional]
Performance: 45 W to 200W
Power (typical): 6.5 Amp DC
Measurements (typical): 0.3 x 3 (45W) to 0.5 x 4 (200W) inches
Calibration loss (relative to NIST): ▒ 2%

LED-Goniometer

During the measurement, the LED is rotating by 180░. This allows the brightness to be measured from various angles. An emission characteristic is captured.

Using the Goniometer tuned specifically to our high speed spectroradiometer, we capture the following measurement parameters:

  • Radiation angle
  • Peak illumination vs. angle
  • Colour coordinates vs. angle
  • Tristimulus values vs. angle
  • Lab/Luv vs. angle
  • Ra vs. angle
  • Relative output vs. angle
  • Peak wave length vs. angle
  • Dominant wave length vs. angle
  • Spectral half value width vs. angle
  • Colour temperature vs. angle
  • Colour saturation vs. angle
  • Radiant power vs. angle

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