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It all started with LW and SW in the early 1990s. BYK-Gardner´s well-known wave-scan analyzes waviness based on wavelength range and its intensity.

The LW-value integrates waviness in the range of 1.2 – 12 mm and the SW-value sums up fine textures in the range of 0.3 – 1.2 mm.  As material and process parameters changed, these integrated parameters were not always sufficient to differentiate various surface appearances.

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Consequently, in 2001 the next generation, wave-scan DOI was introduced measuring 5 wavelength ranges as well as the distinctness of image. These six measurement parameters are graphed  and called a “structure spectrum”, which is an ideal guide for trouble shooting and optimizing surface appearance based on material or application influencers.

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To keep it simple for QC control and management reports 1- or 2-dimensional scales are used. Additionally to LW and SW, OEM specific scales with different target values and tolerances were developed over the years.
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In 2012, a new approach was initiated within the VW/Audi group and was first presented at our BYK-Gardner User Meeting in 2013.

The results are weighted according to the VW / Audi study to simulate an observation distance of 1.5 m.

Since then several visual studies were conducted and it became obvious that observers can distinguish samples based on its dominating wavelengths. In order to determine a specific waviness size, the optical profile of the wave-scan measurement needs to be analyzed with a so-called Fast Fourier Transformation, which is in simple words, a structure spectrum with much higher resolution.
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The result is up to four new scales:
  • Dominant LW wavelength and its maximum amplitude
  • Dominant SW wavelength and its maximum amplitude

  • Dominant LW = 4.6 mm
  • Dominant LW intensity = 25.1

Dominant SW = 1.3 mm
Dominant SW intensity = 13.6

Two dominant wavelengths

Dominant LW = 4.4 mm
Dominant LW intensity = 8.6
Dominant SW = 1.3 mm
Dominant SW intensity = 8.2

Curious? The new firmware is free of charge and available for download in the smart-chart package under:
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