Amplitude measurement of a sinusoidally oscillating object using a frequency-ramped laser diode with some intensity modulation indices

摘要

An optical heterodyne interferometer with a frequency-ramped laser diode (LD) has been constructed for amplitude measurements of a sinusoidally oscillating object. In order to eliminate the effect of intensity modulation without complexity in optical setup, an optical interferometry operating under a small index of intensity modulation has been proposed and its effect on the amplitude measurements of an oscillating object has been analyzed based on spectral analysis of interference beat signal. From the simplified analysis for some ratios of beat frequency to modulation (ramped) frequency and for some intensity modulation indices, it is confirmed that the theoretical analysis and the experimental results are in relatively good agreement.