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OptoFidelity's AR Testing is Now Traceable to VTT MIKES Proving up to 50 Times More Accurate than Conventional Methods

  • The product under validation was OptoFidelity's WG-GAT, a Littrow Diffractometer for measuring AR waveguide grating manufacturing quality.
  • WG-GAT’s measurement accuracy was validated based on measurements performed by VTT MIKES, one of the leading metrology institutes for accurate grating period measurements worldwide.
  • Fully automated WG-GAT measures diffraction grating pitch and orientation and can find grating defects on picometer and arcsecond scale accuracy, making it the preferred choice for AR waveguide testing.

Tampere, Finland - June 27, 2023 - OptoFidelity, a leading provider of advanced AR/VR measurement solutions, is proud to announce the validated measurement accuracy of OptoFidelity's waveguide grating analysis test system, WG-GAT. This achievement was made possible by OptoFidelity's extensive, demand-driven product development and cooperation with VTT MIKES, the National Metrology Institute of Finland.  

Cooperation with VTT MIKES, renowned as one of Europe's foremost metrology institutions, consisted of precise grating period and orientation measurements. These measurements were performed with VTT MIKES' high-accuracy metrology instruments solidifying WG-GAT's measurement accuracy in a traceable, standard way.

"This achievement serves as indisputable evidence that our customers can place their trust in the accuracy and reliability of the grating analyses conducted with WG-GAT," stated Thomas Kerst, Product Manager at OptoFidelity. "WG-GAT's exceptional accuracy and repeatability, along with its traceability to the SI system of units, position it as an unrivaled solution in the industry." 

Unlike AFM and SEM, WG-GAT measures the grating period and relative grating orientation with sub-atom scale resolution, repeatability, and accuracy. Additionally, it is an off-the-shelf and fully automated system, making it the preferred choice for AR device development. 

WG-GAT’s Product Owner at OptoFidelity, Roosa Mäkitalo, emphasized the dedication and innovation within the OptoFidelity team, stating, "We developed WG-GAT based on customer demand. Previously, customers had AFM and SEM technologies available, but they were simply insufficient. In addition to these technologies being expensive and difficult to use, their performance, accuracy included, was inadequate for world-class AR waveguide development. Our customers' feedback and collaboration were invaluable during the development process. We are proud that we were able to transform a laboratory-developed solution into a standardized product that customers can confidently order out of the box." 


Key Benefits and Features of WG-GAT 

  • Fully automated, easy-to-use, off-the-shelf system.  
  • Repeatability of < 10 pm for the grating period and < 10 arcsec for relative grating orientation.  
  • Sub-pm and sub-arcsec measurement resolution.  
  • Designed for precise measurements of AR diffractive waveguides.  
  • Can measure various types of gratings on any substrate, including but not limited to 1D or 2D gratings, surface relief, or volume-holographic gratings.  
  • Can measure samples up to 300 mm in diameter wafer size.  



VTT MIKES is a visionary research, development, and innovation partner for companies and society. VTT is one of Europe’s leading research institutions owned by the Finnish state. They advance the utilization and commercialization of research and technology in commerce and society. Through scientific and technological means, VTT turns large global challenges into sustainable growth for businesses and society. It brings together people, business, science, and technology to solve the biggest challenges of our time.  

VTT has done years of research on improving and calibrating its diffractometer. They are one of the most experienced metrology institutes for grating period measurements in the world.  

Additional research information from VTT in this field: 


Key Findings of the Benchmark

Accuracy of WG-GAT (Littrow Diffractometer)

  • Grating period measurement: ± 50 pm (Applicable for the grating period between 320-425 nm using 405 nm laser, in controlled ambient air conditions).
  • Relative grating orientation measurement: ± 50 arcsec.

Collaboration with VTT MIKES

  • VTT MIKES characterized waveguide samples with their extremely well-calibrated diffractometer, rotary table, and autocollimator. VTT reached the following expanded uncertainty for the measurements:
    • Grating period measurements: 20 pm
    • Relative grating orientation: 1.2 arcsec.
  • OptoFidelity measures the characterized samples with WG-GAT, now having a traceable measurement accuracy for WG-GAT.


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