Light Emitting Diode Spectral Scans & Measurements

Steve J. Noll

This site presents actual electro-optical measurements of commercial Light Emitting Diodes. LED vendors have been known to overstate output powers and guess at beamwidths. Posted here are honest numbers resulting from real measurements using calibrated photometers, spectrometers and goniophotometers.

Measurements of the LEDs were made using the following equipment...

• Spectrometer System:
  • Ocean Optics high resolution model HR4000.
  • 5 micron slit option.
  • L4 collection lens option.
  • HC1 200nm-1100nm grating.
  • UV4 detector window upgrade.
  • FOIS-1 integrating sphere.
  • LS-1-CAL-INT calibrator.
• Luminous Intensity Measurement System:
  • Institute for Photometry & Radiometry (INPHORA) photometric detector, f1'<1.5%.
  • CIE127-1997 condition B setup.
• Total Output Measurement System:
  • UDT Flat Response Detector (for radiometric Watt measurements.)
  • INPHORA photometric detector (for photometric Candela measurements.)
  • INPHORA-calibrated red, green, blue, 880nm and 940nm LEDs.
  • 8-inch Labsphere integrating sphere.
• Radiation Pattern Measurements:
  • Custom Computer-Controlled Goniophotometer.
  • Keithley 2500 Dual Photodiode Meter.
• Keithley 236 Source-Measure Unit for constant current supply and Vf measurements.

UV LED MEASUREMENTS

Vendor	Model	Claimed Intensity	Claimed Wavelength (nm)	Claimed Beamwidth (dg)	Measured Averaged LED Intensity (mcd)	Measured Total Output (mW)	Measured Peak Wavelength (nm)	Measured Spectral Width FWHM (nm)	Measured Beamwidth (degrees)
All Electronics	ULED-2	n/a	395	30	139	11.9	399	12.0	30.4
superbrightleds.com	RL5-UV1230	12 mW	400	30	137	11.9	402	11.7	32.2
superbrightleds.com	RL5-UV2030	20 mW	405	30	146	10.6	398	13.0	20.5

NOTES:
All reading are averages of three LEDs.
Averaged LED Intensity per CIE 127 condition B.
Total Output measured in a calibrated integrating sphere.
All measurements made with 20 mA constant current drive.
Beamwidth measured with an automated goniophotometer.
Yes - the RL5-UV2030 measures about half the claimed power output.

The Goniophotometer I designed and built while Senior Test Engineer at API for measuring emission patterns of LEDs and acceptance patterns of photodetectors. A Keithley 2500 Dual Photodiode Meter is used for both the measurements and driving a stepper motor:

   Other links that may be of interest...

Largest used high-tech equipment dealer directory on the 'net:
Largest used hi-tech equipment dealer directory... http://www.big-list.com

Largest Thermoelectricity information site on the 'net:
Thermoelectricity information site... http://www.peltier-info.com

Homemade Glassworking Lathe:
Homemade Glassworking Lathe... http://www.big-list.com/glasslathe.html

(C) 2006-2014 Steve J. Noll

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