Near-Field Testing of Luminaires€¦ · Title: Nabije-Veld testen van lichtbronnen by Daniel van...

Near-Field Testing of Luminaires by Daniel van Brecht

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)


• 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


LED strip


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


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


Luxmeter

Far-Field

• Polar Plot • IES of LDT file


> 15 meter


Illumination often takes place in the Near-Field

The use of Far-Field data for simulating Near-Field illumination produces incorrect results


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


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


Lens

Shutter Color

Filters

ND

Filters

CCD


2-axis goniometer

Imaging colorimeter


Imaging the luminaire on the CCD


(X,Y,Z)

(x,y,z)

Distinguish individual rays

• Luminous Intensity

• Color (CIE Cx, Cy)

• Point-of-Origin

• Angle


Simultaneous registration of thousands of rays


X Y

Z Start angle luminance intensity

X Y Z Iv

rays

“Radiant Source Model”


Extracting Useful Information


X Y

Z

Ray-tracing to a theoretical surface produces an illuminance pattern



Ray-tracing to the inside of a sphere


Intensity profile along the circumference


Polar plot (IES / LDT file)

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


Advantage of Near-Field Measurement


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.


Total flux: 4299.94 lm Total flux: 4317.7 lm

Far-Field Measurement (External Lab.)

Near-Field Measurement (Radiant Zemax)


• ASAP • FRED • Generic Formats • Integra • Lighttools • OptiCAD • Optis / SPEOS • Photopia • Simulux • Specter • TracePro • Zemax


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


• Measurement of consistency between LEDs (color & luminance)


Luminaire (DUT)

Imaging colorimeter


• IES file generation in seconds

• Extremely high angular resolution

END


Near-Field Testing of Luminaires€¦ · Title: Nabije-Veld testen van lichtbronnen by Daniel van...

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