Accurate measurement of gas lubricated slider bearing separation using visible laser interferometry.

Highly accurate (minimum measuring separation 0.025 μm, accuracy 0.002μm), wide frequency range (dc to more than 100kHz) measurement of the separation of gas lubricated slider bearings is presented using visible laser interferometry. The new technology for realizing this measurement includes ; 1) elimination of undesirable interference patterns by adopting optics that focus the laser beam into a small cavity, 2) elimination of laser tube resonance noise, 3) automatic compensation for variations in the optical parameters. Experiments adopting this measurement are performed in an ambient helium atmosphere and the results are compared with numerical solutions based on the modified Reynolds equation. The experimental and numerical results have excellent agreement within the range of separation down to 0.025μm, and with Knudsen numbers as high as 8. As a result, it is confirmed that the modified Reynolds equation can be used to predict slider bearing characteristics accurately within the experimental range of separation and Knudsen numbers.