flatness measurement - smartSTITCH
The smartWLI systems provide subnanometer resolution for all magnification. With optional xy table up to 300 x 300 mm2 (standard configurations) the extension of the measuring area is easy possible - since the smartWLI systems are - based on the graphic board calculation - extreme fast.
Unfortunately most tables have an error of several μm in z - axis over larger positioning areas. One of the bigger questions is the compensation of the typically limitations of xy tables if you try to stitch multiple scans together. What seems a linear movement is an reality a bigger movement up and down in z direction plus an tilting in all directions:
Stitching result without height and without tilt compensation:
Stitching result with height and without tilt compensation (MountainsMap):
Stitching result with height and with tilt compensation (GBS programmed smartSTITCH):
Summary:
- smartWLI systems using smartSTITCH - combined with an perfect calibration of the curvature of the reference mirror and the EPSI (extended phase shift interferometry) algorithms are able to compensate height and tilt errors from the tables
- without smartSTITCH you can get - even with the height compensation of MountainsMap - complete wrong results
The software extension enables the user of smartWLI systems to solve measuring tasks with several 100 single scans involved more accurate, with higher resolution and with an much more attractive price than competitive solutions which try to improve the results with expensive hardware components.
PS:
In the same way as table errors smartSTITCH is compensating the thermal drift of the sensor in office environments (depending on the used material and the height of the stand app. 1 ... 5 μm per °Celsius).