Abstract
Low-coherence phase-shifting interferometry is presented for measuring spreading of a molecularly thin lubricant film. This method provides lubricant distribution in three dimensions from calculation using phase-shifted two-dimensional interferograms. As light source, low-coherence white light was employed, demonstrating a remarkable effect on suppressing image noise as compared with a laser. The phase-shifting function was realized by attaching a high-precision piezo actuator to the reference surface of the interferometer. To prevent fringe drift induced by mechanical vibration, the signal of fringe position detected by a position sensitive detector was used for feedback control of the piezo actuator. By accurately driving the position sensitive detector, high-precision phase shift was realized even in the presence of vibration. The applicability of the low-coherence phase-shifting interferometry was confirmed by measuring a nanometer-order-thick lubricant film on a diamond-like carbon surface.
