We have previously reported work in the area of fiber probe development at NIST for micro feature measurement. This probe, which we refer to as the Fiber Deflection Probe, functions by optically imaging the stem from two orthogonal directions a few millimeters away from the ball end of the fiber. The probe is well characterized and has demonstrated performance at the sub 50 nm level for diameter measurements. This probe was essentially used as a 2D probe and also only in touch trigger mode. We have since extended the capability of the probe to full 3D measurements and have also made profile measurements in touch-trigger and pseudo-scanning mode. We describe these enhancements in this paper. 3D capability: Along the Z direction, the fiber buckles upon contacting the part. Because the fiber buckles by large amount for a very small displacement along Z, our probe is actually much more sensitive along Z than along X or Y. We therefore achieve full 3D capability by measuring the shift in fiber position due to the buckle. We have measured hemispheres where the pole point is measured using the buckling technique while the other points are measured using deflection technique. Profiling: We have made profile measurements on gage block surfaces in touch-trigger mode (the fiber leaves the surface before each sampling point) and also in pseudo-scanning mode (dragging on the surface we refer to the method as pseudo-scanning because the fiber and gage block are stationary during the imaging process). Because the fiber adheres to the surface, it is not possible to obtain horizontal profiles in pseudo-scanning mode. We have therefore investigated the use of vibration assisted scanning where the fiber is acoustically excited to resonance during the motion of the probe from one sampling location to the next. We have obtained profiles using vibration assisted scanning whose straightness values are in excellent agreement with those obtained using touch trigger mode.
Proceedings Title: Proceedings of the Annual Meeting of the American Society for Precision Engineering 2006
Conference Dates: October 1, 2006
Conference Location: Monterey, CA
Conference Title: Annual Meeting of the American Society for Precision Engineering 2006
Pub Type: Conferences
CMM, dimensional metrology, fiber buckling, fiber probe, profiling