White Light Interferometer (WLI)
For fast and accurate measurement of surface topography over intermediate distances.
The technique: White Light Interferometry (WLI) is a powerful technique for non-contact measurement of surface topography at high vertical and moderate lateral resolution. Almost any surface can be measured, even quite dark ones. A measurement is made in a few seconds.
The instrument: WYKO NT-9800 from Veeco Instruments with an automated sample stage. A number of data processing options are available, making it easy to analyse the surfaces quantitatively. SINTEF has also developed its own software to extract information about specific surface features, such as the depth and tip radius of curvature of notches in a fatigue testing specimen.
SINTEF has further developed the instrumnet hardware and software to enable the study of changes in the local surface topography during process like stepwise etching, electropolishing, corrosion, drying of liquids, etc. These changes can be visulalised in video clips.
The WYKO instrument can be operated in two measurement modes: Phase Shifting Interferometry (PSI) for very flat surfaces and Vertical Scanning Interferometry (VSI) for more rough surfaces. Mode comparison:
Other key features:
|Measurement time per image
||10 s |
||From 62 µm x 46 µm to 4.5 mm x 3.4 mm depending on the magnification. |
Even larger by image stitching (several cm2 possible).
||From 7 µm/pixel down to the diffraction limit (~ 0,5 µm/pixel) depending on the magnification.|
|Detector array size
||640 x 480 pixels|
||Convenient size up to 40 cm x 40 cm, longer samples possible. Height < 15 cm.|
||< 30 kg|
||Minimum 2% reflection. Translucent or layered surfaces can be difficult to measure correctly.|
||Usually none. Might need layer deposition to increase reflection or diffuse scattering.|
Joachim Seland Graff
, phone +47 98 23 04 73 and
, phone +47 98 28 39 46