Pro Lite Technology

Instrument Panel Measurements

Bentley Flying Spur Interior

ProMetric™ imaging photometer is helping bentley to perfect the illumination, colour and brightness of its cars' instrument panels

Bentley Motors produces some of the finest motor cars in the world. You expect a very high attention to detail in the design and production of their vehicles, and this exacting approach extends to the selection of the photometric test equipment which Bentley chose to help in the development of its cars’ interior lighting, instrument panels and infotainment displays.

Bentley has embraced advanced, solid state lighting (SSL) based upon light emitting diodes (LEDs) in its vehicles. These are used extensively for display backlighting, for subtle mood lighting in the cars’ cabins and for illuminating switches and panel indicators. For Bentley, it was vital that the LEDs selected provide consistent illumination, create the required level of brightness (luminance) and emit exactly the desired colour. Visual comparison of the LEDs is extremely subjective and simply cannot quantify the performance of the light source or display. One possible solution would have been a traditional “spot” photometer – a light meter which measures the brightness and colour of a display one (small) spot at a time. However Bentley was interested in a more productive solution.

That solution was an imaging photometer – specifically a ProMetric™ PM-1400 CCD Imaging Photometer made by Seattle-based Radiant Imaging Inc and sold and supported in the UK by Pro-Lite. ProMetric photometers are powerful, CCD-based light and colour measurement instruments that provide for vastly increased productivity compared with traditional “spot” photometers. Whereas a spot photometer can only measure the brightness and colour of one point on a display or light source at a time, a CCD-based ProMetric photometer can measure literally millions of points simultaneously. Moreover, because the ProMetric camera views the whole light source or display at once, localised luminance and colour differences can be easily detected – artefacts that simple spot meters might easily miss.

The attributes of the ProMetric photometer which lead to Bentley choosing this camera over rival systems (or indeed an ordinary video CDD camera) were the PM-1400’s 16,000:1 photometric resolution, full frame CCD sensor (1536 x 1024 pixels), traceable calibration and precise match to the CIE tristimulus observer functions. The PM-1400 provides a high sensitivity with wide dynamic range which means that it will detect colour and luminance differences that the human eye would see but which lesser cameras would miss. The full frame CCD gives accurate measurements of small features and individual LEDs whilst maintaining a wide field of view. The PM-1400’s tristimulus filter wheel more precisely mimics the colour response of the human eye, meaning that the ProMetric camera will report colour differences more accurately.

The power of an imaging photometer can be seen in the images below of an airbag warning light. Please note that this image is for illustrative purposes only - it was not recorded from a Bentley. This shows a true colour bitmap as recorded with a ProMetric photometer on the left. On the right is the same bitmap presented in a false colour scale with a point-of-interest box overlaid. The false colour scale visually exaggerates luminance differences. The mean luminance and chromaticity of the illuminated area of the legend is automatically reported as shown.

Example ProMetric IP Measurement

Overall, the PM-1400 provides colour and brightness measurements which Bentley can rely upon for accurate communication of LED and display performance within its supply chain and – ultimately – has lead to enhanced display clarity and improved interior lighting in its cars. 

Pro-Lite gratefully acknowledges the permission of Bentley Motors to publish this article. For further information on ProMetric CCD imaging photometers, click here.

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