1. Why luminaires need testing
2. Near- versus Far-Field
3. The Far-Field Method
4. The Near-Field Method
5. Extraction of Useful Information
6. Advantage of Near-Field Testing
12/3/2014 Copyright 2014 Radiant Zemax, LLC
• Specification of the source Total flux, Intensity-over-Angle, Color-over-Angle, CCT,
CRI, Glare, EEI
• Lighting Fixture Design Testing for optimization of the light engine, diffusor,
back-reflector, lens, etc.
• Development of a Lighting Plan Downloadable data for Lighting Simulation Software
(e.g. DIALUX, Relux)
12/3/2014 Copyright 2014 Radiant Zemax, LLC
• The majority of the optical information is provided by a single measurement:
measuring light-over-angle using a photogoniometer
• 2 categories of photogoniometers: Far-Field and Near-Field Goniometers
12/3/2014 Copyright 2014 Radiant Zemax, LLC
LED strip Near-Field • The dimensions of the luminaire have
an effect on the illumination pattern
Far Field • Size of the luminaire has no
influence of the light pattern.
• The luminaire is considered as a point-source
12/3/2014 Copyright 2014 Radiant Zemax, LLC
The Far-Field Method
• Old, well established technique
• Measurement far from the source
• Luminaire is considered to be a point-source, emitting light in all directions
12/3/2014 Copyright 2014 Radiant Zemax, LLC
Illumination often takes place in the Near-Field
The use of Far-Field data for simulating Near-Field illumination produces incorrect results
12/3/2014 Copyright 2014 Radiant Zemax, LLC
The Near-Field Method
• State-of-the-Art technique, made possible by modern CCD cameras and PCs
• The light source is described by many rays of light
• Measurement results are valid in both the Near- and Far-Field
• Applicable on both small sources (LEDs) and large luminaires
12/3/2014 Copyright 2014 Radiant Zemax, LLC
Provides everything that Far-Field measurement provides
+ Extra
Accurate results in the Near-Field
Compact setup (small laboratory)
Export data to ray-tracing software
+ + Extra (same equipment)
Testing uniformity (color & luminance)
Single-shot IES file generation
12/3/2014 Copyright 2014 Radiant Zemax, LLC
(X,Y,Z)
(x,y,z)
Distinguish individual rays
• Luminous Intensity
• Color (CIE Cx, Cy)
• Point-of-Origin
• Angle
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X Y
Z Start angle luminance intensity
X Y Z Iv
rays
“Radiant Source Model”
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X Y
Z
Ray-tracing to a theoretical surface produces an illuminance pattern
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Angular distribution - incl. export IES / LDT files
Color-over-Angle
Total flux (lumen rating)
Unified Glare Rating (UGR)
Correlated Color Temperature (CCT)
Energy Efficiency Index (EEI)
Color Rendering Index (CRI) - optional
Source Uniformity
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Far-Field Data Near-Field Data
Fixture with 10 LEDs / Different lenses Light pattern on a parallel plane, 3cm from the fixture. Ray-tracing with Zemax software.
12/3/2014 Copyright 2014 Radiant Zemax, LLC
Total flux: 4299.94 lm Total flux: 4317.7 lm
Far-Field Measurement (External Lab.)
Near-Field Measurement (Radiant Zemax)
12/3/2014 Copyright 2014 Radiant Zemax, LLC
• ASAP • FRED • Generic Formats • Integra • Lighttools • OptiCAD • Optis / SPEOS • Photopia • Simulux • Specter • TracePro • Zemax
12/3/2014 Copyright 2014 Radiant Zemax, LLC
Past Present Future
Test Requirements CCT, CRI, EEI
IES/ LDT files ; lighting simulation Ray sets (LED) ; luminaire design
Ray Sets (light engine) ; luminaire design Ray Sets (luminaire) ; lighting simulation
Lumen Rating Angular Distribution
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• Measurement of consistency between LEDs (color & luminance)
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Luminaire (DUT)
Imaging colorimeter
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• IES file generation in seconds
• Extremely high angular resolution
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