THE FUTURE OF LIGHT MEASUREMENT

Pieter Kramer - Laser 2000 Benelux

THE FUTURE OF LIGHT MEASUREMENT

Pieter Kramer - Laser 2000 Benelux

History of light measurement

Mid 1850’s, Bunsen’s photometer

Photometry measures light radiation in terms of perceived brightness to the human eye. Main characteristic of light is luminous flux.

Late 1960’s, photometers and lux meters

1980’s first mirror Gonio photometers

Angular distribution

Around 1920The first integratingsphere

Integrating spheres

Adding a spectrometer to a integrating sphere gives more data

Spectrometer

LumenColor temperatureCRI

Results and further considerations

Pros:• Good for measuring incandescent bulbs and 4pi sources.• Fast and accurate total spectral luminous measurements

Cons:- Takes a long time for a single measurement incl. setup.- Directional lights can give large errors (7-10%)- Linear lights needs huge spherical dimensions- Lamps can heat up in sphere- No 3D information (no IES/LDT files)

Integrating spheres

PhotoGoniometers

Integration sphere: lumen values + colorimetric data if using a spectrometer

Goniometer: Angular distributionIES, LDT

The most used solution brings all the photometric data, IES and LDT files

Angular distribution is of high importance for the lighting industry: manufacturers, designers and engineers need this information for 3D modelling.

Environmental concerns call for new regulations

Example from EULumen from a directional lamp must only be measured in 90° or 120° cones.

Definition of a directional lamp: At least 80% of the light is radiated into a fixed beam angle (90° or 120° cones).

Cannot be done in an integrating sphere

New EU regulations: sometimes not possible to use sphere

New developments in measuring luminaires

Typical systems include a photo-sensor, goniometer and a spectrometer

New technology: Future proof all-in-one measuring solution includes spectrometer and a goniophotometer

Photometer

Spectrometer

Color deviation along the beam, intensities in PPFD and much more.

• Light distribution curve• Beam angle• IES and LDT files• Luminous flux (lumen)• Light intensity (candela)• CRI, TM30, CQS• CCT• Integrated Spectrum• Power and power factor• Efficiency (lm/watt)• UGR• PPF• PPFD• Color deviation

Spectrogoniometers measuring all parameters

3D visualisation

Integrated spectrum

Beam angleData from a spectrogoniometer:

IES and LDT

Future proof IES and LDT files with color information

So what about the international standards for luminaire measurements?

IESNA approved methods for light metrology

LM-9 electrical and photometric of fluorescent lampsLM-20 photometric testing of reflector type lampsLM-45 electrical and photometric of general service incandescent filament lampsLM-51 electrical and photometric of high intensity discharge lampsLM-54-99 lamp seasoning LM-58LM-59 guide to spectroradiometric measurementsLM-66 electrical and photometric of single ended compact fluorescent lampsLM-78 total luminous flux of lamps with integrating sphereLM-79 electrical and photometric of solidstate lighting productsLM-80 lumen maintenance of LED light sourcesLM-82 electrical and photometric charcaterisation of SSL lamps as a function of temperature (LM82 is the LM-79 but then at elevated temperatures).

USA IESNA LM79 Standard

Pros:• Lamp mounted in operating position• Both up and down measurements• Fluorescent + high pressure sodium lamp

Cons:- Takes a long time for a single measurement- Difficult to operate- Need a large black room- Large footprint + rack- Stray light can occur- Long distance to sensor (mirror)

- Nearfield goniometer not recognized by any standard- Difficult to include spectrometer

Mirror goniometer Nearfield goniometerOld requirement of LM79 is strict, because of big change in classical fluorescent and high pressure sodium lamp at different orientations.

However, mirror goniometer setup not practical

Mirror goniometers are not easy to operate and install

NOW: CIE S 025 International standard

Globalizations calls for international standards.

Many of the most demanding requirements:

About S 025

Total or partial luminous flux Luminous efficacy Luminous intensity distributions Center-beam intensity Luminance and luminance distribution Chromaticity coordinates CCT, CRI and angular color uniformity

Measurement techniques other than explicitly mentioned are acceptable if demonstrated equivalent

Defined test conditions (like env and module temperatures, air flow, supply voltage) with nominal value and tolerance interval

User has to set up an uncertainty budget according to ISO/IEC guide 98-3 or CIE 198

Standard test conditions and tolerances

S-025 allows orientation correction

SSL luminaires may be measured in different orientation than designed orientation

Measurement + correction step = conforming standard

Horizontal measurement correction

But the drop in lumen is no more than 0 – 1.2%

Lm

min

Monitoring the lamp from operating position

• Stabilize in operating position• Move to measuring position• Measure the change in output

High power lamps with directional heatsinks tend to change the most

An example: deviation in lumen

Deviation in lumen on the tested objects when orientation was changed to horizontal was between 0.47 – 0.99%

A comparison from DTU(Technical University of Denmark)

Everybody seems happy with the S 025 and NEN 13032-4

because it allows common sense.

It makes SSL luminaire measurements easier and less expensive.

CIE S 025 makes measuring more “relaxed”

Pros:

• DUT in non-operating position• Easy to operate• Fast measurements• No need for a black room• Small footprint• Can operate in ambient light• No big racks• Only a computer is needed

Use common sense:

- Lamp is being rotated- Stray light can occur- distance to sensor

Lamp dia x 5 - 15

Type-C Horizontal Goniometer

New standard now allows for movement of LED lamps

Measurement area is more “relaxed”

Black room is now only necessary around the goniometer, using a directional sensor.

Features that could be implemented

Automation of frequent user interactions? Addition of a Photodiode to measure Flicker with the gonio?

Integration of TEC heatsink on the gonio?

Software guided orientation correction protocols?

Ra color fidelity values in polar plots?

Automatic determination of number of C-planes?

Extention to UV and NIR? Photobiological safety?

What would YOU like to have measured?

Luminaire light metrology is now SOFTWARE driven

Thank you for your attention !

THE FUTURE OF LIGHT MEASUREMENTPieter Kramer - Laser 2000 Benelux

THE FUTURE OF LIGHT MEASUREMENTPieter Kramer - Laser 2000 Benelux