Hybrid light source for scanning white light interferometry-based MEMS quality control

Ville Heikkinen, Kalle Hanhijärvi, Juha Pekka Aaltonen, Heikki Räikkönen, Ben Wälchli, Tor Paulin, Ivan Vladislavov Kassamakov, Kestutis Grigoras, Sami Franssila, Edward Haeggström

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


We apply a hybrid light source with adjustable spectrum to Scanning White Light Interferometric MEMS device characterization. The source combines light from a blue laser (409 nm), a fluorescent material (emission peak 521 nm), amber LED (597 nm) and cyan LED (505 nm) to cover the visible wavelengths. The Gaussian spectrum of the light source reduces interference ringing and improves surface localization, which is important when imaging diffuse surfaces or layered structures. The new light source allows both stroboscopic illumination and spectrum shaping during a measurement. Changing the illumination spectrum allows one to maximize the reflection from the measured surface - compared to reflections from other surfaces - as a mean to improve signal-to-noise-ratio. To validate the source we measured static MEMS samples featuring known step heights using the light source at three different mean wavelengths (508 nm, 524 nm and 579 nm). The measured step heights (7.029 ± 0.045 μm, 7.002 ± 0.041 μm and 7.005 ± 0.056 μm) were close to those measured using a halogen lamp (7.025 ± 0.020 μm). Interferograms without the side lobes typical for white LEDs were achieved. The FWHM of the interferogram of the combined light source was (1.859 ± 0.008 μm).
Original languageEnglish
Title of host publicationOptical Measurement Systems for Industrial Inspection
Number of pages8
Place of PublicationMunich
Publication dateMay 2011
Pages80822O-1 - 80822O-8
Publication statusPublished - May 2011
MoE publication typeA4 Article in conference proceedings
EventOptical Measurement Systems for Industrial Inspection VII - Munich, Germany
Duration: 23 May 2011 → …
Conference number: 7

Publication series

NameProceedings of SPIE

Fields of Science

  • 114 Physical sciences
  • Scanning White Light Interferometry
  • LED
  • laser
  • fluorescence
  • quality control
  • MEMS

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