Advantages of LED technology
by Lukas Pescoller, 27.07.1999

FAG-VRG has started in 1995 to study the LEDs as a possibility to improve conventional densitometers and spectrofotometers in terms of stability, life time, robustness, measurement speed, industrial manifacturing etc. and has presented on Imprinta in 1997 the first densitometers (FAG ScanPen, FAG Vipdens 444) based on LED technology. Nowadays most of the measurement devices distributed by FAG are based on this new, revolutionary LED technology.

1 Advantages

1.1 industrial manifacturing becomes easier
The mechanics and electronics of an LED based optic is much more simple than the mechanics of lamp based optics because of several reasons:

  • LEDs have already a narrow light emitting angle. Therefore there is no need to add special optical or mechanical components like lenses, reflectors etc. to focus most of the emitted light to the measurement patch.
  • the light of LEDs is 'monochromatic'. These effects that the reflected light has not to be splitted for filtering purpose by mirrors, or optical fiber or any other, costly optical or mechanical components
  • the revers order of monochromaticity (monochromatic light source, white receptor) results in one single electronic (fotodiode, logarithmic unit etc.) which is common to all colour channels (Cyan, Magenta, Yellow, etc.). Only one third (in case of 4 colour densitometer) of electronic components is needed compared to the conventional, lamp based, technology, where there has to be a seperate electronic (or at least part of it) for each channel.

1.2 quality of LED based units
Because of the simplier mechanics and electronics, errors in assembling can be avoided. So the LED technology fits perfectly to the FAG logo: Simply perfect, perfectly simple. Moreover there are some side effects that improve the quality of the LED based units.

  • an extreme long life time (about 200.000 hours) combined with a high measurement speed results in a high stability in terms of emitted light. Example: one LED is on for about 10ms per measurement. If we make about 500 measurements a day, 200 days a year, 10 years, then the LED is on for about 2:48 hours out of possible 200000 hours!
  • LEDs have high intensity in terms of emitted light. In adition the entire emitted light can be reflected and will be measured by one single fotodiode (no optical splitting of light). With the conventional technology the reflected light had to be tailored, a certain percentage for each colour channel. Therefore LED technology results in more light, higher signals, higher resolution and more stable measurement results.
  • a short measurement time results in low load to filters. Filters will be exposed to light for 2:48 hours only in 10 years!
  • Low current consumption will make the units smaller: two batteries will produce enough current for some hundred thousends of readings.
  • higher direction independence than with lamps will make the units simplier (one LED instead of 2 lamps)

2 Chances

2.1 New products
With the LED technology there can be developed new products with new specifications because of the simplicity of the optics, the low current consumption, the direction independence, smaller apertures, low costs, extreme long life time

  • scanning densitometers and spectrofotometers (FAG Scan Pen and Speedy Eye) need extrem short measurement time, extreme long life time, and extreme low current consumtion of LED technology because there will be made much more measurements as with normal densitometers or spectrofotometers.
  • low cost spectrofotometers and multiple colour densitometers (FAG Vipdens 2000) with 'monochromatic' LEDs instead of expensive grids for environments where robustness is verry important (press room, embedded units etc.)

2.2 Marketing
Production of competitive units in terms of

  • price
  • robustness
  • size
  • independency (battery driven)
  • guarantee of 3 years