Pro Lite Technology

NFMS Near-Field Goniophotometer for Testing Luminaires




A compact & affordable luminaire goniophotometer which generates standard IESNA & EULUMDAT photometric files 

The PM-NFMS from Radiant Imaging combines a motorised goniometer stage with a ProMetric CCD imaging photometer to perform a near-field angular analysis of the luminance and colour from LEDs, luminaires and solid state lighting. ProSource software then scales this to far-field luminous intensity data from which standard photometric files are generated (IESNA, EULUMDAT). So-called photometric data defines how much light a luminaire emits and into what directions; lighting designers then use this standardised data format with a variety of commercially-available lighting design programmes to determine the number and positioning of luminaires in order to create the desired illuminance (lux level).

The Near-Field Difference

The measurement of luminaires has traditionally been performed with an illuminance meter placed in the photometric far-field which views the light source at one angle of azimuth and elevation at a time. The device under test is mounted on a motorised goniometer stage (the "goniometer") and the photometer views the lamp from a distance of between 10 and 25m, the actual working distance depending on the size of the light fitting. The cost of a typical far-field goniophotometer system (combined with the associated, large dark room) was often prohibitive, which meant that most manufacturers have used the services of independent test laboratories. The PM-NFMS goniophotometer changes all this by exploiting the latest advances in imaging photometry to make luminaire measurements more accessible and affordable.

Rather than using an illuminance meter in the photometric far-field to record the illuminance as a function of angle, the PM-NFMS employs a ProMetric CCD imaging photometer to record spatially-resolved images of the near-field luminance emitted from the light source. Luminance (units of cd/m2) is the optical property one measures when working up close to the light source. Spatially-resolved images of the source luminance are recorded in Radiant Imaging's proprietary ProSource (.rs8) format for one angle of azimuth and elevation at a time. The associated, motorised goniometer stage scans the device under test over ± 88° in all directions. Radiant Imaging's ProSource software then performs a ray-tracing operation to scale the near-field luminance readings to equivalent far-field illuminance values at the click of a mouse. Standard photometric files in the IESNA (.ies) and EULUMDAT (.ltd) format can then be generated. The photometric data reported also includes the light output ratio (LOR, a measure of the efficiency of the luminaire) as well as the integrated luminous flux (units of lumens).

Return on Investment Measured in Months

The benefits of near-field goniophotometry are numerous:

  • Being a near-field measurement, the dark room required is much smaller than for a traditional far-field installation. The room size depends upon a number of factors but plan on a laboratory meaasuring no more than 5 x 5m. This greatly reduces the facilities cost necessary to perform luminaire measurements.
  • The cost of the near-field goniophotometer system hardware is also a fraction of the price of a traditional far-field installtion. The PM-NFMS can pay for itself compared with the costs associated with having samples tested independently after a few tens of measurements.
  • Standard photometric data is generated automatically. To compile such data manually would be an extremely time consuming and error-prone process.
  • Having access to an in-house test facility means that new products can be brought to market more quickly and at lower cost. With PM-NFMS, there's no need to wait weeks if not months to obtain your photometric data.
  • Product development cycles are reduced and new innovations tested quickly to establish their feasability. PM-NFMS enhances your ability to innovate and gives you a distinct competitive advantage.

Goniometer Frames for Small, Medium & Large Luminaires

The PM-NFMS goniometer frame is available in three sizes to accomodate different sizes of luminaires. The maximum size and weight of the device under test determine which goniometer frame you will need. As a guide, the medium size PM-NFMS0800 has been used to measure luminiares measuring up to 1.6m linear and weighing up to 25kg. The compact PM-NFMS0400 is suitable for samples weighing up to 5kg and measuring up to 80cm approximately. The minimum sample size that a frame can accomodate is determined only by the field-of-view of the ProMetric imaging photometer and this can be selected through appropriate choice of lens. For guidance on selecting the the right size PM-NFMS goniometer frame for your luminaires, contact Pro-Lite.

The ProMetric CCD Imaging Photometer/Colorimeter

ProMetric imaging photometers are available with a range of sensitivities and CCD pixel resolutions, from 10-bit to 16-bit (the ability to resolve from 1,024 to 65,536 levels of brightness) and from 512 x 512 up to 3,072 x 2,048 pixels. Interchangeable lenses are available to match the field-of-view of the imaging photometer to the size of the device under test. For the majority of applications, the ProMetric PM-1200N-1 represents the best compromise between price and performance. This is a 12-bit (4096 grey scale) photometer with 1,392 x 1,040 pixels and spectral response precisely matched to the CIE 1931 2° standard tristimulus observer function. The internal RGB filter wheel is paired with a neutral density filter wheel which allows the PM-1200N-1 to cope with a wide range of light levels without risk of saturation. ProMetric software for the imaging photometer is also included which allows for the use of the PM-1200N-1 for spatial luminance and colour analysis of sources, including signs and LED arrays.

Specifications & Ordering Information

Goniophotometer Frames

PM-NFMS-0400

PM-NFMS-0800

PM-NFMS-1500

Approx. Max. Linear Luminaire Length (mm) *

800

1600

**

Recommended Max. Luminaire Weight (kg) *

5

25

**

Recommended Max. Luminaire Size (mm) *

460 x 385

865 x 535
600 x 600+

**

Max. Luminaire Size for Recessed Fittings (mm) 365 x 290 700 x 355 **
Goniometer Size (W x D x H, mm)

900 x 360 x 600

1200 x 750 x 750

1200 x 800 x 1800

Operating Footprint (mm) ***

970 x 970

1400 x 1400

1780 x 1780

Approximate Weight (kg)

25

40

360

Operating Range, Azimuth

± 90°

Operating Range, Elevation

± 90°

Angular Precision

0.25°

Power

220V, 50Hz

System Configuration  

PM-NFMS Goniometer Frame

PM-NFMS0400, -0800 or -1500

ProMetric Imaging Photometer

The PM-NFMS is compatible with any ProMetric CCD imaging photometer / colorimeter

Recommended Photometer

PM-1200N-1

   Type

Uncooled CCD with internal RGB & ND filter wheels

   Pixel Resolution

1392 x 1040, interline transfer

   Dynamic Range

12 bits (4096:1)

   Photometric Range ++

0.05 ... 100,000 cd/m2

   Spectral Response

CIE 1931 2° tristimulus observer (XB filter optional)

   Field-of-view

Lens dependent

Software Supplied

ProMetric PM 9.x, PM-NFMS, ProSource

Choice of Lens(es) +++

8 ... 300mm, Nikon compatible

Calibration(s), NIST-Traceable

Luminance (cd/m2)

 

Standard CIE illuminant A / D65 colour corrections

Accessories Included

Heavy duty tripod with 3-axis geared head

 

Laser alignment device

 

Illuminance photometer or colorimeter

Services Included

On-site installation & operator training

 

Software & technical support licence, 12months

User-Provided

Dark room

 

Computer, PC

 

Table or support structure for goniometer frame

Measurement Parameters

vs. J, f

   Axial Luminance

Lv (cd/m2)

   Axial Luminous Intensity

Iv (cd)

   Integrated Luminous Flux

Fv (lumens)

   Light Ouput Ratio

LOR (%)

   CIE Chromaticity 

xy, u'v'

   Correlated Colour Temperature

CCT (Kelvin)

   Colour Difference 

Du'v'

Native Data Formats

Radiant Source Model (.rs8)

Export Data Formats

IESNA (.ies)

 

EULUMDAT (.ldt)

 

*      Maximum sample sizes & weights quoted are approximate - please confirm suitability of your chosen NFMS
       goniometer frame when ordering.
**    NFMS-1500 specifications pending.
***   Operating footprint varies with sample size.
+     The PM-NFMS0800 can be used to measure a 600 x 600 2D luminaire, mounted off-axis.
++   Photometric range quoted is approximate and depends upon the spectral power distibution of the sample.
+++ One lens and lens calibrations is included with the goniophotometer system. Please consult Pro-Lite for
       assistance with lens selection.

Related Products
Tour Our Demo Lab

Pro-Lite has a demonstration dark room to allow clients to see the NFMS imaging goniophotometer as well as our integrating sphere photometers in action. Visitors are always welcome - use our enquiry form to request a tour.

We have also posted a video tour of our lab on YouTube.

Further Information
Case Studies
Knowledge Base

> Measurement of Light
> NFMS White Paper               

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